6.47pmTonight's game is crucial for Paulo Bento's side, who trail Russia by four points in the race for automatic qualification to Brazil 2014. Nothing but a win is good enough.
6.50pmNorthern Ireland, on the other hand, have no hope of reaching their first World Cup since Mexico 1986. They have six points from their six games so far, which puts them in fourth place, five points behind Israel.
6.54pmRight, let's give you some team news from Windsor Park...
7pmCristiano Ronaldo starts for the visitors, as does Fabio Coentrao, who was said to be heartbroken after his last-minute loan move to Manchester United fell through on transfer deadline day.
7.02pmMeanwhile, Michael O'Neill has made three changes to the side that beat Russia 1-0, with Aaron Hughes, Craig Cathcart and Daniel Lafferty being replaced by Jonny Evans, Chris Brunt and Lee Hodson.
7.06pmNorthern Ireland came so close to victory when these two sides met in the reverse fixture in October last year. Niall McGinn had given his side a lead that looked like sticking until Helder Postiga struck late on to deny Michael O'Neill's boys a famous victory. The two nations also faced each other in an international friendly back in 2005, which also ended 1-1.
7.15pmThe win over Russia was only Northern Ireland's second in their last 23 fixtures. However, Windsor Park is bouncing in anticipation of Cristiano Ronaldo and company. The fans smell another upset, which would put a huge dent in Portugal's hopes of finishing top of the group and qualifying outright.
7.25pmClick here to read more about the changes for Northern Ireland this evening.
7.28pmNorthern Ireland 1-0 Russia - Martin Paterson's winning goal:
7.30pmPortugal 1-1 Northern Ireland - Helder Postiga spares blushes late on at the Estadio do Dragao:
7.36pmO'Neill has spoken of the importance of making life difficult for Bento's talented squad tonight. In the pre-match press conference, he said: "It's important they have a difficult night and that they know from the word go that they're going to have a difficult night. I think it would be foolhardy of us to go and play a really open game and say to Portugal 'come and play us, you attack us and we'll attack you'."
7.38pmMeanwhile, Bento himself said that he has taken warning from NI's momentous 1-0 victory over Russia, stating: "Northern Ireland have a chance, so maybe it is possible that they attack a bit more. The Russia match was another warning. We knew this match would be tough but that game and the way they beat Russia showed that they're a really strong squad. It was a warning for us."
7.40pmWe're just five minutes from kickoff at Windsor Park. Anticipation is high as this man prepares to take the field.
7.42pmSeen by many as the best player in the world - rivalled only by the genius that is Lionel Messi - what does the Portuguese powerhouse have in store for us tonight?
7.45pmThe Portuguese anthem is observed impeccably, although the singing of the players leaves a lot to be desired. Only Chris Brunt and Jonny Evans join as 'God Save the Queen' rings around the stadium.
7.48pmRaul Meireles, known as a somewhat wacky character, is sporting a fierce beard these days. It's truly something to behold. Andyway, we're ready for kickoff...
2 minFirst touch from Ronaldo and it results in a tackle that brings rapturous applause from the Irish fans.
3 minPortugal are seeing plenty of the ball in the first few minutes. Raul Meireles receives possession around 25 yards from goal and, never shy in winding up, tries to bend one beyond Carroll but gets it all wrong.
6 minIreland get down the pitch for the first time in the match. Shane Ferguson and Chris Brunt try to make something happen down the left but the West Brom winger's cross is easily caught by Patricio.
8 minThis Irish players are all over the pitch at the moment, nipping at the heels of the Portuguese team. Martin Paterson in particular is giving Pepe plenty to think about early on. The noise at Windsor Park is deafening.
10 minPortugal are nearly caught out by a ball over the top, but Pepe gets across to tackle Jamie Ward, which results in the first corner of the match.
12 minBrunt slings a long free kick into the box and McAuley goes up with Patricio but the referee blows his whistle as the goalkeeper fumbles the ball.
15 minFantastic footwork from Ronaldo, who is booed when in possession. He makes mince meat of Steven Davies before laying the ball off to Coentrao on the halfway line. Nothing gained, but impressive none the least.
16 minOliver Norwood is penalised for a foul on Ronaldo. I wonder if the Huddersfield Town player used to clean his boots when he was a part of Manchester United's youth team...
16 minCLOSE! Bruno Alves is left unmarked as Joao Moutinho sends the resulting free kick into the box, but the defender plants his header wide of the target. A warning sign.
18 min"One Gareth Bale! There's only one Gareth Bale!" chant the Northern Irish fans. I'm not sure if it's wise to try and wind Ronaldo up, but what the hey...
21 minGOAL! Northern Ireland 0-1 Portugal (Bruno Alves)
21 minQuestion marks surrounding Carroll on that one, as another Moutinho set piece ends with Bruno Alves having a go at goal. It was a corner this time, cleared only to the edge of the box where Alves was waiting to put his team into the lead with a side-foot volley. Good technique, but it wasn't the most powerful of efforts.
24 minSAVE! Lovely play down the left from Portugal, with Coentrao and Vieirinha combining to great effect. The Wolfsburg winger cut inside and got a shot away, but Carroll got down well to save at his near post.
28 minBuoyed by the goal, Portugal are really controlling possession now.
30 minCHANCE! Portugal threatening a second, on this occasion exploiting the right flank. The ball nearly breaks for Meireles just yards from goal, but the Irish defence scramble clear.
32 minCHANCE! Coentrao tries to be too cute deep in his own half and that allows Davis to get a cross in for Paterson, but Alves is on hand to hack clear.
36 minThe hosts are starting to exert some pressure but Patricio has not yet been tested. Norwood nearly finds Paterson at the back post but Pepe puts it behind for another corner.
36 minGOAL! Northern Ireland 1-1 Portugal (Gareth McAuley)
36 minWhat a superb corner from Shane Ferguson, surpassed only by the header from McAuley! The West Bromwich Albion defender towered above Bruno Alves, Cristiano Ronaldo and Helder Postiga to direct a header into the far corner. Windsor Park erupts!
40 minThe boot of Moutinho and the presence of Alves means that Portugal are a real threat from set pieces.
41 minSHOT! Postiga has a dip from around 25 yards but drags it well wide of the goal and losing his footing in the process. Poor effort.
43 minHow pathetic of the Valencia striker, who is sent off for a 'headbutt' on Gareth McAuley. The pair squared up after a tangle and Postiga pushed his head into the face of the West Brom defender. It was nothing, but it was right in front of the referee, who showed no hesitation in brandishing the red card. Ronaldo has also gone into the book for his protests.
8.37pmWhat an end to an entertaining first half at Windsor Park. Michael O'Neill will rightly feel that his team can pull off another shock as he talks to his players at half time. I don't think he'll need to say much, they're really fired up tonight.
8.44pmClick here to read the story of the first half.
8.46pmShould Portugal lose tonight, would it be too dramatic to suggest that Postiga's petulance has severely dented their hopes of finishing top of Group F? Ifs, ands and buts at the moment, of course.
8.48pmPortugal dominated possession, especially early on. However, the home side have risen to the challenge and have enjoyed spells of pressure themselves. Only the one shot on goal, but it's one that has them level.
8.49pmOn the other hand, Paulo Bento's men have carved out a few decent opportunities. They have a job on their hands to pull a result out though.
8.50pmRight, the players are back on the pitch. Ready for the second half?
45 minPORTUGAL GET THE GAME BACK UNDERWAY AT WINDSOR PARK!
46 minRonaldo tries to thread a ball through for Pereira but Hodson cuts it out. The rain is really lashing down in Belfast now, but the atmosphere hasn't dampened.
48 minBrunt drives into the area and wins a corner, which he then swings into the near post for McAuley. This time Alves wins the battle of the centre-halves, but Ireland have retained possession.
50 minCLOSE! Cheeky effort from McAuley, who spots Patricio slightly off his line and tries a chip from a long way out. Everyone at Windsor Park is straining their eyes to see if he is Pele in disguise.
52 minJamie Ward teases the Portuguese defence with a dangerous cross that Pepe is forced to head behind for another corner.
52 minGOAL! Northern Ireland 2-1 Portugal (Jamie Ward)
52 minWindsor Park is rocking as the home side profit from another corner! This time is was Jonny Evans who beat Alves to the near-post ball, flicking it on for Ward to bundle the ball over the line. There are suspicions of offside as the dejected Portuguese players trudge back into position for the kickoff, although Patricio should really have done better.
57 minReplays confirm that Ward was clearly offside when Evans flicked the ball on. They also confirm that Patricio was desperately weak in his efforts to deny Ward lashing into the net.
58 minBOOKING! Bruno Alves goes into the book for a deliberate handball. Chris Brunt lines up the free kick, but Patricio gets behind his driven effort.
60 minCoentrao hangs a ball up for Alves but Carroll shows Patricio how to deal with pressure by picking it out of the air.
61 minThe West Brom winger was late into a challenge on Joao Pereira and receives his second yellow card. He's devastated as he walks off the pitch, as that's evened up the sides and given Portugal a massive boost.
65 minPORTUGAL SUB: Nelson Oliveira comes on to replace Vieirinha.
67 minSAVE! Veloso unleashes a powerful drive at goal but Carroll shows strong hands to beat the ball away. Great effort, even better save.
68 minGOAL! Northern Ireland 2-2 Portugal (Cristiano Ronaldo)
68 minHe's been quiet for most of the evening, but the Portuguese captain gets his name on the scoresheet. It's the fourth goal of the evening, and it's a fourth goal from a corner. Ronaldo got in front of his marker to power home at the near post.
71 minNORTHERN IRELAND SUBS: Kyle Lafferty comes on for Niall McGinn, while Jamie Wards makes way for Corry Evans.
76 minSAVE! Nani - on the pitch for Raul Meireles amid the drama of Brunt's red card - has a shot, which moves in the air quite a bit. However, Carroll gets enough behind it to keep his side on level terms. Portugal are now camped in Ireland's half pushing for a winner.
76 minGOAL! Northern Ireland 2-3 Portugal (Cristiano Ronaldo)
76 minStatic defending from Northern Ireland, which allows Ronaldo to double his tally for the evening and get his team back in the lead. He was left completely unmarked in the box, giving him space and time to plant a header into Carroll's net.
80 minA third red card of the evening and it's all going wrong for the home side now. Lafferty charged down Pereira, and although he was late the Valencia defender did make a meal out of it. Surely game over now.
83 minGOAL! Northern Ireland 2-4 Portugal (Cristiano Ronaldo)
83 minHe was hardly in the game before he scored the equaliser and now he has a hat-trick. Remarkable. This time it's from a free kick, which the Irish really could have avoided. Oliveira did well to make space in the wall before peeling away, allowing Ronaldo's shot a clear path. It took a slight deflection on it's was past Carroll.
88 minIt's all gone quiet at Windsor Park. An upset was definitely on the cards tonight. Brunt's red card was certainly the turning point but Ronaldo might argue otherwise.
90 minPORTUGAL SUB: Ronaldo is coming off and he will be replaced by Ruben Amorim. He's been the difference tonight.
90 minFour minutes to be added on, but I think the Irish fans just want it to be over now.
90+2 minPereira dives in the area as a cross comes in and gets a telling off from Carroll. The Valencia defender caught blatantly cheating there and smirks as he runs away. Wind-up merchant.
9.42pmValiant effort from Northern Ireland, but a Cristiano Ronaldo-inspired Portuguese team emerge triumphant and retake top spot in Group F. They're two points ahead of Russia now but have played one game more.
9.43pmThat's all from us at Sports Mole - thanks for joining us and we hope to see you back again soon!