Both of these players headed into their encounter at the O2 Arena in London knowing that defeat would all but end their chances of reaching the semi-finals of the ATP World Tour Finals.
The history books made Juan Martin Del Potro the favourite, having won all three meetings between the two.
As it was, the Argentine ended up cruising to a two-set victory tonight over Janko Tipsarevic.
Below is our minute-by-minute updates of how the match unfolded.
7.30pmEvening all. This may not be the most mouth watering of matches on paper, but it's straight knockout tennis which should hopefully bring out the best in both players.
7.32pmNo disrespect to Tipsarevic, but Del Potro is the bigger name of the two. The Argentine is a Grand Slam winner thanks to his success over Roger Federer at the US Open in 2009. From the the viewpoint of the neutrals, I think Del Potro would be the preferred winner.
7.33pmHe didn't start the competition too well though thanks to a three-set loss against David Ferrer on Tuesday night.
7.35pmThere was also a defeat for Tipsy during the opening round of matches. In truth, he was comfortably beaten by Roger Federer. However, he would have gone into that match knowing that his best chances of a victory would come against tonight's opponent and Ferrer, rather than R-Fed.
7.36pmThe history books would tell you that another defeat is heading Tipsy's way tonight though. In three meetings with JMDP, he's yet to win.
7.38pmThey first met in Miami back in 2009, where Del Potro claimed a 6-4 6-1 win. Then in 2011 at Delray Beach the Argentine come through 6-4 6-4.
7.39pmTipsy finally won a set against Del Potro in a Davis Cup clash in September of last year. However, it wasn't enough to prevent him from slumping 5-7 6-3 6-4.
7.44pmWe've just seen shots of Sergio Aguero at the O2, who will be supporting his fellow countryman Del Potro. He knows a lot of footballers! A couple of years ago he had Carlos Tevez in his corner. Does this mean that Del Potro is a Manchester City fan?!
7.45pm"It's a very important match. We both know that if we lose there's not much chance to qualify. He's very good in the attack and serve. I'm going to try to be the more aggressive player," Tipsarevic tells Sky Sports News.
7.46pmDel Potro adds: "It's going to be a tough match. I believe in myself and my ability to come through."
7.47pmHere comes the players. Tipsarevic will be introduced to the crowd first.
7.51pmWell, well. Del Potro wins the toss but decides to receive the serve. That's a strange decision in my opinion. He's a big server and you'd expect him to want to get off to a good start. Perhaps he fancies an early break.
7.56pmWe will be underway shortly. The two players are just going through a few service routines. By the way, Tipsarevic has broken two rackets already! Hope he's got plenty with him!
7.59pmTipsarevic gets us off and running at the O2 Arena...
8.00pmOh dear! Del Potro has three break points...
8.01pmACE! That's one saved by Tipsy in the best possible manner.
Del Potro *1-0 TipsarevicBREAK! But it's only a slight restbite for Tipsy as an unforced error gives JMDP an early break. Tipsy really didn't look comfortable there. We know he hasn't been well. Let's just hope he can continue and make a game of this.
8.06pmBreak point to Tipsarevic as Del Potro goes long...
8.06pmACE! Consider that well and truly saved by Del Potro! Deuce.
Del Potro 2-0* TipsarevicTipsy goes wide with a shot he really should have made and Del Potro has an important hold. It's a missed opportunity for the Serbian.
8.11pmTipsarevic goes into the net and again he faces a break point...
Del Potro *3-0 TipsarevicBREAK! This could be over very quickly. Tipsarevic does not look to be at the races today. He goes long and 'Del Boy' is three games in front.
Del Potro 4-0* TipsarevicThis is far too easy for Del Potro at the moment. He serves out to love. What's worse for Tipsy, he's broken a string on yet another racket. That's three already!
Del Potro 6-0 0-0* TipsarevicACE! SET! Well this is all too easy for Del Potro. Fair enough he's hitting his targets and playing some good shots, but Tipsy is not putting up much of a fight. The way it's going, I'd be surprised to see Tipsy finish this match. He doesn't look to be himself.
8.33pmBut Del Potro spurns the chance by firing into the net. Deuce.
Del Potro 6-0 *0-1 TipsarevicWell that was hard work but eventually Tipsy holds! I don't think there has been a bigger cheer at the O2 all week. Let's hope that inspires him to make a game of this now.
8.39pmWould you believe it? Following a smash, Tipsarevic has broken another racket. That's four! Madness.
Del Potro 6-0 *1-2 TipsarevicNone whatsoever is the answer to that question! It's a love service game would you believe. And to add to that, he's also had two of his broken rackets mended. Things are looking up!
Del Potro 6-0 2-2* TipsarevicIt's a nice easy hold for Del Potro. Tipsy is yet to make any inroads on his opponent's serve. Still, at least he is competitive now.
8.51pmBreak point Del Potro. We've been here before...
Del Potro 6-0 *3-2 TipsarevicBREAK! That could well be curtains as far as Tipsarevic's chances are concerned. He hits long and Del Potro has yet another break. That's got to hurt.
9.17pmIt only took one hour and 16 minutes for Del Potro to claim a vital win there. He now has a fighting chance of reaching the semi-finals, although he'll probably have to beat Roger Federer on Saturday. It will be a surprise if we see Tipsarevic again in this competition. He looks to be really struggling with the after affects of his recent virus.
9.19pm"I'm trying to play my best tennis. It's not easy to win 6-0 because he is a very good player. I will try to beat Federer now," Del Potro tells Sky Sports News during his post-match interview on the court.
9.21pmThat's just about all we have time for this evening. We'll be back tomorrow though for Tomas Berdych vs. Novak Djokovic in the afternoon, before Andy Murray comes up against Jo-Wilfried Tsonga. Coverage will start at around 1.15pm. See you then.