The pair lost their 100% records in a five-set epic on Centre Court that was won by number one seed Djokovic.
Read how one of the greatest matches ever unfolded in our minute-by-minute updates below.
12.31pmGood afternoon sports fans! It's one of the best days of the tennis calendar, it's men's semi-final day at Wimbledon!
12.33pmFrom a completely neutral, non-British perspective this first semi is the more mouthwatering of the two. Djokovic has been in irresistible form at the All England Club. He's yet to drop a set. However, if Del Potro isn't carrying an injury he could really trouble the Serb this afternoon.
12.36pmIn the last round Del Potro played phenomenally to knock out fourth seed David Ferrer. The Argentine fell awkwardly in the first game and his body language suggested that he would have to retire. He managed to plough on though and hit the ball so cleanly to defeat last month's French Open finalist in straight sets.
12.39pmDespite this, Djokovic is still big, big favourite to win today. As mentioned, he's yet to lose a set, reaching the last four with a comfortable victory over seventh seed Tomas Berdych on Wednesday. The Czech was far from his best that day though and Del Potro should present a tougher challenge as long as he's not injured.
12.41pmIf Del Potro is injured then Djokovic's doggedness and tactical nous will probably be too much for the Argentine. More of his heavy hitting will just come straight back and he could simply get worn down by the number one seed.
12.43pmWEATHER WATCH! It's the hottest day of the Championships so far as this heatwave that has been promised to the UK finally arrives. Temperatures are around the 24-degree mark and that is good news for Del Potro. As a big hitter, his shots will travel through the air just a bit quicker, taking some of the returning time away from Djokovic.
12.48pmThe other semi-final involves British hope Andy Murray and Poland's Jerzy Janowicz. Second seed Murray is the heavy favourite there but if 6'8" Janowicz serves as he has throughout the tournament then it will be a tough day at the office for Muzza.
12.51pmSince the early exits of Roger Federer and Rafael Nadal, a Djokovic-Murray final has been touted as the obvious match on Sunday. Even though both men are hardly worth backing with the bookies, I expect Del Potro and Janowicz to trouble both. I'd be very surprised if we have two straight-set victories from the top two seeds.
12.54pmAhead of this weekend's finals, we here at SM have looked back at the top five Wimbledon finals ever. Find them here. No prizes for guessing which is top!
12.57pmON THIS DAY: Going even further back in tennis history. July 5 marks the exact date that America's Arthur Ashe became the first black man to win Wimbledon in 1975. Our very own Matt Domm looked back on a momentous moment. His piece is here and a great read it is too with a fantastic picture of Ashe.
12.59pmPREDICTION TIME! The two Ds, Djokovic and Del Potro, are on their way down to Centre but just before they emerge, it's time for my prediction. I have to go with Djokovic, but I expect Del Potro to grab at least one set.
1.02pmThe last time these two met it was Del Potro who won in Indian Wells in March this year. Their last meeting on grass also went the Argentinian's way in the bronze-medal match at the Olympics, which were also held at the All England Club. Plenty of encouraging signs for Juan Martin.
1.04pmDel Potro is also likely to be the neutrals' favourite inside Centre today so could gain inspiration from that.
1.05pmCELEB SPOT! The Royal Box at Centre Court is always awash with famous faces and today I've already spotted Stefan Edberg and boxer Amir Khan.
1.08pmThe umpire today is Britain's James Keothavong. He announces that Del Potro won the toss and elected to receive. An odd choice that as you'd expect the Argentine to want to impose himself right from the start.
1.10pm"Time," says umpire Keothavong. Both men jog back to their chairs for final water bottle preparations and what not. Centre Court is nice and full already, here we go.
1.11pmThe two trade forehands on the opening point before Del Potro finds the net to hand the opening point to Djoko.
1.11pmDel Potro with a little slip on the next point but it's nowhere near as bad as the one that had him floored in the quarter-final. He's fine.
Djokovic 1-0* Del PotroDel Potro gets his first point at 40-0 down with some heavy hitting before Djokovic seals the first game with his first ace on the next.
1.14pmDel Potro begins his service game with an ACE of his own.
1.15pmWe have our first challenge of the match from Del Potro at 30-0. Hawk-Eye reveals that his forehand was a fraction out.
Djokovic *1-1 Del PotroA plane soars over Centre Court as Del Potro's serve takes off and Djokovic can't get it back. Confident holds from both men to start.
Djokovic 2-1* Del PotroDjoko goes one better than the opening game by holding to love, wrapping up the game with a lovely one-two punch. He kicks a serve out to Del Potro's backhand before arrowing a backhand winner down the line. Gorgeous.
1.21pm"Ay ay ay!" berates Djokovic to himself after misfiring with a backhand.
Djokovic *2-2 Del PotroThe two Ds continue to go stride for stride as Del Potro also holds to love. Whose serve will be the first to crumble?
Djokovic 3-2* Del PotroAnother simple hold for Novak. Del Potro showed intent by getting on top of one second serve but could do little else in that game.
1.26pmSurprisingly, Djokovic has already made four unforced errors with Del Potro yet to make one. The Serb has hit eight winners to Del Potro's two though. Many would have expected those stats to be the other way round!
1.27pmAs the players change ends for a third time Djokovic pops on a baseball cap because of the sunlight at the opposite end to the Royal Box.
1.28pmDjokovic challenges a Del Potro first serve that was called in and he's right to do so as it was just long. Del Potro then DOUBLE FAULTS and is in a bit of trouble at 30-30.
1.30pmDjokovic comes out on top in an extended rally on the next to earn break point but it's saved by Del Potro with a booming serve down the middle that Djoko can't return.
1.31pmExcellent rally between the two at advantage Del Potro that is won by Djokovic due to a clever forehand. He took all the pace off it but got some ridiculous angle.
1.33pmMatch of the Day presenter Gary Lineker on Twitter: "Djokovic is some player, but I'm not sure the cap suits him." I agree, Gary. He looks a bit nerdy.
1.35pmDel Potro has now seen three chances to hold serve go as both men hammer the life out of the ball before Djokovic again goes to that angled crosscourt forehand and Del Potro's win-or-bust reply slaps the net.
1.36pmSurprising time for a light-hearted moment as Del Potro double faults on another game point and lets out a yell of frustration.
Djokovic *3-3 Del PotroFINALLY Del Potro comes through after five deuces as Djokovic's backhand whizzes just wide.
1.40pmAn absolute rocket of a forehand from Del Potro and he's 15-30 ahead on the Djokovic serve. 102mph that groundstroke was. Astonishing power.
Djokovic 4-3* Del PotroDjokovic wins the next two points thanks to a pair of first serves and we remain on serve in this opening set. Can Del Potro now have a simple service game of his own? He won't want the sort of battle he had in his last.
1.44pmGoodness me, that's an impressive stat for Djokovic. He's won all 14 points where he's got a first serve in. Del Potro? 13 of 15. Not bad either.
1.46pmSuperb volley from Djokovic as he tries to surprise Del Potro but it's only an OK approach and Del Potro returns with interest. His backhand is low but Djokovic lunges to his left and pulls off a volley winner. 30-30.
Djokovic *4-4 Del PotroDel Potro holds to 30 as Djokovic hits out and then into the net with a pair of backhands. It's perhaps his best shot normally but isn't quite firing today. Yet.
1.48pmThis stat really surprises me. Winners: Djokovic 11-3 Del Potro. That is partly because Djokovic will get more of Del Potro's balls back than anyone else on tour but also because Del Potro is going for broke like he usually might.
Djokovic 5-4* Del PotroDjokovic races to 40-0 but is pegged back to 40-30 as Del Potro showcases his backhand. The Serb holds on the next point with a viciously kicking serve out wide. It's now up to DelPo to hold to stay in the set.
1.55pmDel Potro is looking comfy at 30-0 but we're back to 30-30 now as Del Potro launches a forehand down the line but it doesn't get past the net.
Djokovic *5-5 Del PotroDel Potro with a rare winner to seal the game and what a shot too. He goes for broke with a run-around forehand down the line and it just catches the back edge of the baseline. Great shot.
1.57pmAn unimpressive start the 11th game of the match as Djokovic is again wide with his usually-reliable down-the-line backhand.
1.58pmIt then looks like Del Potro has moved 0-30 with a flashy forehand but it zips just wide. The line judge had called it in but umpire Keothavong overrules.
Djokovic 6-5* Del PotroAn entertaining point to finish the game at 40-15 as Djokovic goes for the drop shot. Del Potro just gets there but is then lobbed and his through-the-leg 'hot dog' shot doesn't come off. Can the Argentine now hold and send us to a tie-break, or will Djokovic break at the final opportunity?
2.03pmSHOT! Del Potro moves to 30-0 as Djokovic wildly misses a down-the-line backhand AGAIN. On the next Del Potro smashes a forehand to the corner and it should be a winner but somehow Djokovic digs out a backhand that goes for a winner itself.
2.05pmSET POINT Djokovic...
Djokovic 7-5 *0-0 Del PotroSET! That could be huge. Del Potro with a good deep second serve but his forehand to the corner just goes wide. He challenges but it's more in hope than expectation. What a killer blow for the Argentine.
2.07pmFair play to Djokovic. Del Potro was going along swimmingly in that game until that stunning winner from Djokovic which just turned the tide. To win four points in a row against a serve like Del Potro's at a crucial time like that is so impressive.
2.09pmHow will Del Potro be faring mentally? It's not an encouraging start to the second for the eighth seed as he loses out on the baseline to Djokovic's 15th winner. DelPo has just four.
Djokovic 7-5 1-0* Del PotroA hold to 15 to begin the second set for NoDjo. Because of that last-gasp break in the last, he again has the slight advantage of serving first.
Djokovic 7-5 *1-1 Del PotroThere's a BIG winner from DelPo. He unleashes a forehand up the line to move to 40-15 and then follows that up with an unreturnable serve to level up the set.
2.17pmDel Potro turns up the heat on his backhand but Djokovic still has a point to hold serve at 40-30.
Djokovic 7-5 2-1* Del PotroHe does so with a bit of luck, serving out wide before a forehand pops up off the net cord and lands right on the sideline.
Djokovic 7-5 *2-2 Del PotroA love-hold for Del Potro and this second set has taken on a similar pattern to the first. Neither man offering much to their opponent on serve.
Djokovic 7-5 3-2* Del PotroNoDjo matches DelPo in holding to love, finishing off the game with the simplest of smashes. He's yet to offer the Argentinian a single break point.
2.27pmIffy start to the sixth game of the set for Del Potro as he shoots long with a forehand but makes up for it with a massive serve on the next that even Djokovic can't handle.
2.28pmTWO BREAK POINTS for Djokovic...
2.29pmDel Potro saves the first with a brilliant volley as Djokovic looked to pass down the line. The Serb claps his opponent, nice.
2.29pmAnd the second is saved as well with Del Potro's second ACE.
2.31pmDjokovic prevents Del Potro holding and now has a third break point of the game...
2.32pmAgain it goes begging as the Serb produces a rare mishit and the ball flies miles long. You feel that this is now a massively important game.
Djokovic 7-5 *3-3 Del PotroDel Potro saves a fourth break point with an unreturnable serve before coming through as Djokovic hits wide with a forehand.
2.35pmSHOT! Del Potro is down to 58% of first serves in and he'll have to improve that if he is to avoid Djokovic threatening so heavily. He begins the next game with perhaps the shot of the match. Way out of position he somehow blasts a forehand down the line and Djokovic can only watch as it shoots past him.
2.37pmTHREE BREAK POINTS FOR DEL POTRO!
Djokovic 7-5 3-4* Del PotroBREAK! Where did that come from?! Del Potro with a magnificent game there and he's really fired up. At 30-0 he showed fantastic agility to reach Djokovic's drop shot and flick it for a winner, also getting the crowd on his side with an exuberant celebration.
2.42pmDel Potro's shots seem to have a bit more zip all of a sudden and he moves to 40-0 but we're back to 40-30 now as the Argentinian double faults for a third time.
2.43pmAnd now back to deuce! What a turnaround this would be if Djokovic broke straight back.
2.44pmThe Serb does have a BREAK-BACK POINT...
2.44pmBrilliant from Del Potro to save it. He rifles a backhand to the corner and of course Djokovic gets there but the world number one can do nothing about the following volley.
Djokovic 7-5 *3-5 Del PotroDel Potro comes through after squandering the 40-0 lead. He's now one game away from levelling this match up at one set all.
2.46pmI've just spotted a few spare seats in Centre Court. Whoever's sitting there, get back quickly! Fools.
Djokovic 7-5 4-5* Del PotroSome way for Djokovic to show that breaking his serve won't be easy again. He rattles off four unreturnable serves and tells Del Potro: 'Go on then mate, you serve it out.'
2.49pm124mph serve down the middle to start. Djokovic gets his racket there but can't get it over the net.
2.49pmNow 30-0 as Djokovic just hits wide. He challenges but it's no good.
2.50pmFabulous touch from DelPo as he answers Djokovic's drop shot with a more delicate one of his own. THREE SET POINTS...
Djokovic 7-5 4-6 *0-0 Del PotroSET! Djokovic frames the return and that's the second set. What a game we have on our hands now.
2.54pmIt's by far the hottest day of the tournament so far and both men are panting heavily after a long rally that Djokovic wins. Del Potro has definitely increased the intensity of his groundstrokes from that first set though.
Djokovic 7-5 4-6 1-0* Del PotroDjoko is once again the man serving first in the third set and he edges ahead with a hold to 15.
2.58pmA loose forehand from Del Potro and he's behind on serve at 15-30 here.
Djokovic 7-5 4-6 *1-1 Del PotroThree straight points for the Argentinian after that though and he's on the board in the third.
3.02pmDjokovic smoothly advances to 40-0 on his serve but is now a little edgy at 40-30 after a dodgy backhand.
Djokovic 7-5 4-6 2-1* Del PotroA heavy forehand from Djokovic just lands in the corner and Del Potro can't lob it back into play so the Serb holds.
3.04pmMany of the stats are in Djokovic's favour but it's an even game and that is represented by this stat. Total points won: Djokovic 77-75 Del Potro.
3.05pmDel Potro with some Djokovic-esque defence to get back some of the Serb's groundstrokes before he takes the initiative with a bullet backhand that Djokovic can't return himself. 30-0.
Djokovic 7-5 4-6 *2-2 Del PotroFine hold from Del Potro there. He wraps up a love-hold with a blasé backhand winner up the line.
3.08pmA roar of delight from Del Potro as Djokovic goes long with a backhand after a brutal rally. DelPo looking dangerous at 0-30. Six points in a row.
3.09pmGutsy from Djoko as he delivers two unreturnable serves, including a 112mph second serve, and we're back to 30-30.
3.11pmDjokovic ACES to move to game point but we're now at deuce as Del Potro is extremely fortunate in getting a dead net cord off the return.
3.11pmDjokovic's forehand also clips the top of the net but doesn't pop over the other side and it's BREAK POINT DelPo...
3.12pmThe Argentinian doesn't get Djokovic's serve back and it's deuce.
Djokovic 7-5 4-6 3-2* Del PotroDjoko comes through that tough service game, celebrating with an intense fist pump. He knows that that was a big hold.
3.17pmDel Potro looks in disbelief as his forehand at 30-0 slaps the net. He struck it well and must have have thought that it was on its way for a winner.
3.18pmMagnificent in-to-out angle from Del Potro on a pressure point at 30-30. Outrageous.
3.19pmDjokovic returns with intent on the next and it's getting tense now at deuce.
Djokovic 7-5 4-6 *3-3 Del PotroDel Potro again lives with Djokovic from the baseline before the Serb goes for broke and hits wide with a forehand.
3.23pmHello hello! Del Potro has TWO BREAK POINTS as Djokovic opts to go for a winner down the line when he was on the backfoot and doesn't pull it off.
3.24pmThe first goes begging for DelPo as he approaches the net but volleys into the net. He makes the crowd like him even more by putting the ball over the net with his hand.
3.25pmAgain he goes on the offensive but his up-the-line backhand fizzes just wide. Unlucky!
3.27pmDjokovic then has the chance to hold after three straight points but Del Potro says 'no chance!' with a scintillating backhand winner.
Djokovic 7-5 4-6 4-3* Del PotroAnother sensational rally between the pair is won by Djokovic to open up game point. He takes it this time with more vicious groundstrokes. That's another massive hold for Novak. He's the man hanging on in this set.
3.33pmDel Potro has really been playing up to the crowd since his confidence rose. He moves to 40-15 after another gripping rally and fist pumps to no-one in particular, just the Centre Court crowd as a whole.
Djokovic 7-5 4-6 *4-4 Del PotroIt's another easy hold for Del Potro. Can he challenge the Djokovic serve once again?
3.36pmWe're a little over halfway into the third set and Djokovic has just made his first double fault. 15-15.
3.37pmDjoko is behind at 15-30 and Del Potro guesses right on the Serb's approach but he can't pass him at the net as Djokovic lunges to his right and gets it in.
Djokovic 7-5 4-6 5-4* Del PotroAgain Djokovic proves his mettle with a tough hold. Will DelPo now feel the pressure knowing that a stumble here will gift his opponent the third set.
3.40pmNot a good start for the Argentinian as he nets a forehand and then dumps an easy backhand into the net. Djokovic smells a break.
3.42pmWHAT A SHOT! Djokovic is about to earn two set points but somehow Del Potro swats a completely flat forehand back across court. Incredible shot and so unconventional.
Djokovic 7-5 4-6 *5-5 Del PotroWhat a hold that is from the Argentinian. He wins four points on the trot after going 0-30 down, sealing the game with a booming serve that NoDjo can't control.
3.46pmDjokovic wrongfoots Del Potro with an in-to-out forehand to move 40-15 ahead. The Argentinian slips and everyone's a little concerned but he's back on his feet.
Djokovic 7-5 4-6 6-5* Del PotroDjokovic has his first comfortable hold for a while. We're now at the stage where in the first set Djokovic snapped Del Potro's serve to snatch the set.
3.49pmIt's 0-30 and the Serb is looking menacing.
3.50pmNow THREE SET POINTS for the number one seed...
3.51pmDel Potro saves the first two. Massive point coming up now.
3.52pmUNBELIEVABLE! Del Potro smashes down a giant serve but Djokovic plonks the return deep. That should give him the advantage in the rally but somehow Del Potro pulls off a down-the-line forehand winner. Given the circumstances, that's one of the best shots I've ever seen.
Djokovic 7-5 4-6 6-6(*0-0) Del PotroThree set points saved. We're now into a tie-break.
THIRD-SET TIE-BREAKDjokovic 1-0* Del Potro
THIRD-SET TIE-BREAKDjokovic 1-1* Del Potro
THIRD-SET TIE-BREAKDjokovic *1-2 Del Potro. We're still on serve in the breaker.
THIRD-SET TIE-BREAKDjokovic *2-2 Del Potro
THIRD-SET TIE-BREAKDjokovic 3-2* Del Potro
THIRD-SET TIE-BREAKDjokovic 4-2* Del Potro. Oh dear! Del Potro should put the point away but hits an overhead straight back to Djokovic before missing the next smash.
THIRD-SET TIE-BREAKDjokovic *5-2 Del Potro. Djokovic is now two mini-breaks ahead and has two serves for the set.
THIRD-SET TIE-BREAKDjokovic *6-2 Del Potro. FOUR SET POINTS FOR DJOKOVIC.
Djokovic 7-5 4-6 7-6 0-0* Del PotroSET! Del Potro knows the set is gone so just goes hell-for-leather on the return. He puts it in but of course Djokovic is there to guide the ball into the open court.
4pmWhat a huge blow that is for Del Potro. He was the more dangerous man throughout the set but then made it to the tie-break by saving three set points in the 12th game. It was even in the breaker until he made that error with the smash and that seemed to be the turning point.
4.04pmDjokovic nips off for a bathroom break just before the start of the fourth. He's one set away from the Wimbledon final.
4.06pmDel Petro plays two fantastic points to start the fourth but somehow he's 0-30 down as Djokovic displays his supreme defence with Del Potro all over the net.
4.09pmDel Potro recovers well from that, continuing to not hold back on groundstrokes and move to 40-30 and game point.
Djokovic 7-5 4-6 7-6 *0-1 Del PotroHe nets a forehand on the first but earns another chance to hold and this time he converts as Djoko's forehand slaps the tape. Three hours of play we've had now and in this heat it's such hard work.
Djokovic 7-5 4-6 7-6 1-1* Del PotroDjokovic holds his serve just about at 40-30. One thing's for sure, Del Potro won't give up despite what was sure to be a heartbreaking loss in that third set.
4.16pmDel Potro eases to a 40-0 lead but now we're at 40-30 after a wild forehand from DelPo. Can Djoko bring it back to deuce?
Djokovic 7-5 4-6 7-6 *1-2 Del PotroNope. A forehand from Djokovic this time doesn't make it into court and Del Potro similarly hangs on to his serve after being pegged back to 40-30.
Djokovic 7-5 4-6 7-6 2-2* Del PotroAn assured hold of serve from Djokovic there, completing the game with his 14th ACE of the match. Incredibly, DelPo has just two.
4.24pmThere's a hint of familiarity about this as Del Potro is again pegged back from 40-0 to 40-30. Can Djokovic take this game to deuce?
Djokovic 7-5 4-6 7-6 *2-3 Del PotroAgain, no. Del Potro steps into a backhand and Djokovic spoons it back for the Argentinian to put away the winner.
4.26pmAs with the previous three sets, neither man has been able to break serve in the early stages of the set.
4.27pmFeisty start from Del Potro as he hits a forehand that for once Djokovic can get nowhere near. 0-15.
4.29pmMore cheekiness from Del Potro as he reaches Djokovic's volley but his flick up the line just goes long. The Argentinian's momentum carries him to the other side of the court and he asks Djokovic if it was out and the Serb, of course, says that it was. Del Potro gets even more playful by unzipping Djokovic's polo shirt!
Djokovic 7-5 4-6 7-6 3-3* Del PotroDjokovic holds his serve by getting in plenty of first serves and not giving his opponent a look-in.
4.32pmDelPo mishits a forehand and it loops high to the baseline. Djokovic decides to take it on the rise and finds a winner into the corner to move 15-30 ahead.
4.33pmA fatigued forehand from Del Potro and it's TWO BREAK POINTS for Djoko...
4.34pmWhat a point! Both men trade the ascendency before Del Potro comes into the net and pulls off a low volley. Superb stuff. One break point left.
Djokovic 7-5 4-6 7-6 *4-3 Del PotroBREAK! Del Potro finds a first serve but it's returned with intent from Djokovic. Del Potro sends the ball out to Djokovic's forehand and he swipes it back to the baseline, with Del Potro unable to handle it. Is that going to be enough for Djokovic? All he has to do now is hold serve twice and he'll be in the Wimbledon final.
4.38pmHe's not there yet! A backhand down the line just misses and it's 30-30 on the Djokovic serve.
4.39pmA loose forehand from the world number one and DelPo has a BREAK-BACK POINT...
Djokovic 7-5 4-6 7-6 4-4* Del PotroBREAK! This is just fantastic! Neither man holds back in the rally but it's Del Potro who prevails with a backhand down the line that dips into the corner.
4.41pmDjokovic begins the next game with TWO return winners. How on earth has he pulled those off?! 0-30.
4.43pmDelPo wins the next three points though and now has a game point.
Djokovic 7-5 4-6 7-6 *4-5 Del Potro"VAMOOOOOS!" bellows the Argentinian as Djokovic's return flashes wide. Who would have thought two games ago that Djokovic would be serving to stay in the set?
4.46pmBludgeoning forehands from both men to start the 10th game of the set and it's Del Potro who wins the rally as Djoko nets.
4.47pmDel Potro goes for the jugular down 30-15 and his forehand is almost too quick to even see if it's gone out. The line judge says that it has and Hawk-Eye confirms this.
Djokovic 7-5 4-6 7-6 5-5* Del PotroDel Potro hits a mighty forehand winner to save the first game point but doesn't win the second as another forehand is called out. He should have challenged though as Hawk-Eye shows that it did catch the baseline.
4.51pmDjokovic misses with two backhands and that's so unlike him. DelPo at 40-0.
Djokovic 7-5 4-6 7-6 *5-6 Del PotroHe wraps up the love-hold as NoDjo carelessly hits a forehand return long. The Serb will again have to hold to stay in the set and send us into another tie-break.
4.54pmGoodness gracious me, Del Potro's forehand is just breathtaking. He's just flashed another bullet to bring it back to 30-15.
Djokovic 7-5 4-6 7-6 6-6(0-0*) Del PotroThat can't inspire him to a break and we're into a tie-break.
FOURTH-SET TIE-BREAKDjokovic *1-0 Del Potro
FOURTH-SET TIE-BREAKDjokovic *2-0 Del Potro. DelPo's throwing this away like the last set. He rifles a forehand but Djokovic somehow gets it back to the baseline. Del Potro already thinks that the point is over though and he has to challenge but it's wrong.
FOURTH-SET TIE-BREAKDjokovic 2-1* Del Potro. He responds and we're back level in the breaker.
FOURTH-SET TIE-BREAKDjokovic 3-1* Del Potro. Djoko instantly restores the mini-break.
FOURTH-SET TIE-BREAKDjokovic *3-2 Del Potro. Now it's Djokovic who gets a challenge horribly wrong. He's still a mini-break up.
FOURTH-SET TIE-BREAKDjokovic *4-2 Del Potro. ACE from Djoko and we change ends with the serve holding that slight advantage.
FOURTH-SET TIE-BREAKDjokovic 4-3* Del Potro. DelPo's mighty forehand is too good for NoDjo and we're back on serve now.
FOURTH-SET TIE-BREAKDjokovic 4-4* Del Potro. More monstrous hitting from DelPo.
FOURTH-SET TIE-BREAKDjokovic *5-4 Del Potro. The advantage is Djokovic's once more after another just phenomenal rally. Djoko now has two serves for the match.
FOURTH-SET TIE-BREAKDjokovic *6-4 Del Potro. TWO MATCH POINTS...
FOURTH-SET TIE-BREAKDjokovic 6-5* Del Potro. Unbelievable stuff from both men! This is turning into an all-time classic. 24 strokes in that last rally.
FOURTH-SET TIE-BREAKDjokovic 6-6* Del Potro. Magnificent confidence from Del Potro to not hold back there. This is just brilliant.
FOURTH-SET TIE-BREAKDjokovic *6-7 Del Potro. SET POINT DELPO!
Djokovic 7-5 4-6 7-6 6-7 *0-0 Del PotroSET! Del Potro goes for it on the Djokovic return and his crosscourt backhand can't be got back by Djokovic. I don't know how he's done it, but we're into a fifth set.
5.12pmJust as the fourth set starts the game clock ticks into the fifth hour. We could be here for another four hours at this rate.
Djokovic 7-5 4-6 7-6 6-7 1-0* Del PotroDjokovic doesn't want to hang around though. He begins with a love-hold, sealing it with a rare serve-and-volley.
5.17pmHe's done this a few times, our man Del Potro. He blitzes to a 40-0 lead but is now back at deuce after some weary shots.
Djokovic 7-5 4-6 7-6 6-7 *1-1 Del PotroHe doesn't let that slump get to him though, winning the next two points to get on the board in the fifth.
Djokovic 7-5 4-6 7-6 6-7 2-1* Del PotroYou would expect Djokovic to have the better fitness of the two and be able to outlast Del Potro here. He's now won eight out of eight points on serve in this set after another love-hold.
5.21pmHere's Oliver Brown, sports writer for the Telegraph, on Twitter: "Best Wimbledon match since the 2008 final." Hard to disagree with that.
5.23pmDjokovic's trademark up-the-line backhand has been far from its best this afternoon but he's just found a beauty to bring it back to 15-15.
Djokovic 7-5 4-6 7-6 6-7 *2-2 Del PotroDelPo holds to 15 with just his third ACE of the match. Djokovic has 19.
5.25pmAnd now 20 as he opens the next game with one out-wide.
5.26pmDel Potro ends a run of 10 straight points for Djokovic on serve with a wrongfooting forehand. 30-15.
5.27pmDel Potro must be feeling the pace but he's sticking around. Blasting his way to a point to peg Djoko back to 40-30.
5.28pmAstounding return winner from DelPo and we're at deuce. Pressure on Djokovic now.
5.29pmThe Serb hits out with a simple forehand and it's BREAK POINT DELPO...
5.29pmThat's grit worthy of a champion from Djokovic. He finds a first serve and puts away the following backhand.
5.30pmAn ace brings up game point but he follows that with just his second DOUBLE FAULT. Back to deuce.
Djokovic 7-5 4-6 7-6 6-7 3-2* Del PotroTwo more unreturnable first serves from the number one seed so he manages to hold under pressure from Del Potro. The Argentinian is now receiving some massage treatment from the trainer at the change of ends.
5.33pmHere's a great stat from @ITF_Tennis on Twitter: "The @delpotrojuan v @DjokerNole semi is the longest #Wimbledon men's semi-final in history! Previous longest was Becker v Lendl 1989 (4:01)."
5.35pmDjokovic berates himself for allowing Del Petro to reach his backhand crosscourt at 15-15.
5.36pmBREAK POINT DJOKO...
5.37pmSaved! Del Potro goes deep with his backhand, putting Djokovic on the back foot and the Serb can't put it back over.
Djokovic 7-5 4-6 7-6 6-7 *3-3 Del PotroDjokovic threatened there but he couldn't take it and there's some real signs of frustration from the Serb. Can he regain his composure with new balls in his hand to serve?
5.41pmBlimey, that's as close to out as you can get. Del Potro challenges a mishit return and Hawk-Eye shows that a nanometre of the ball was touching the line when it landed.
Djokovic 7-5 4-6 7-6 6-7 4-3* Del PotroThat reprieve can't spur on the Argentinian though as Djokovic holds to 15.
5.42pmOnce again there's been no breaks of serve in the opening games of the set. We're approaching the business end now. Who will crack? Or will we be here all night?
5.45pmHow have they still got this energy?! Djokovic defends unbelievably at the baseline before taking control of the point with a drop shot and lobbing Del Potro to finish. The Argentinian has to slump over and catch a breather. 15-30.
5.46pmTWO BREAK POINTS DJOKO...
5.47pmHe hits long on the first.
Djokovic 7-5 4-6 7-6 6-7 *5-3 Del PotroBREAK! Del Potro's superb down the line backhand puts him in the ascendency but he then misfires with a forehand to hand Djoko the break. The Serb will now serve for the match.
5.49pmHe hits wide with a backhand to start. You would have wanted to win the first point there.
5.49pmA similar missed backhand and it's 0-30. Surely he's not going to throw it away again like he did in the last set?
5.50pmDjoko stays composed on an easy volley to avoid slipping to 0-40.
5.51pmA poor return barely reaches the net from DelPo and it's on the wire at 30-30.
5.52pmBREAK-BACK POINT DELPO!
5.53pmWhat drama! Del Potro's return flicks off the top of the net but Djokovic stays super-cool with a drop shot.
5.53pmMATCH POINT DJOKO...
Djokovic 7-5 4-6 7-6 6-7 6-3 Del PotroGAME, SET AND MATCH DJOKOVIC!
5.55pmThe Serb wins it with a backhand down the line. That shot has been faltering all afternoon but it pays off when it matters most.
5.55pmThe two gladiators embrace at the net. Well done to Djokovic but you have to feel sorry for Del Potro. It's his best-ever run at this tournament and really that match was worthy of a final.
5.57pmThis was definitely one of the best matches of all time. Next up for the Centre Court crowd is there hero - Andy Murray. Imagine having a ticket for the great arena today!
5.58pmTotal match time: Four hours, 43 minutes. Total points won: Djokovic 190-178 Del Potro.
6pmDjokovic has now been involved in two of the greatest matches ever in the last couple of months. His five-set epic against Rafael Nadal in the French Open semi has been described as the greatest clay-court match ever. That day he lost but he's won today and is in his second Wimbledon final.
6.01pmThat's all we've got time for on this commentary. Thanks for joining SM. Our coverage of the other semi will be live on site shortly so look out for that.