Last Updated: 22/01/12 5:58pm
That's it as the final whistle blows and United win 2-1 at Emirates Stadium thanks to Welbeck's winner.
Welbeck makes a pacey run as United look for another but he runs out of legs in the box and is shut down by the Gunners backline.
There's claims for handball against Evans as Mertesacker tries his luck with a shot but replays show the ref was right to play on.
What was I saying? So close for the Gunners as Van Persie charges forward and almost nods the ball into the back of the net.
Evra is ruled offside as Park tries to find him with a long pass down the right. Arsenal aren't showing signs of pushing for a comeback and the seconds are counting down.
Arshavin concedes a free-kick in the middle of the park - not what the Gunners are looking for at this minute.
Five minutes of stoppage time are added and it's not all over for Arsenal just yet. Van Persie lofts in a free-kick but Smalling gets his head to it to clear.
Rosicky lofts a long ball into the box from the right, meant for Van Persie, but Evra is there to nod it clear.
Have Arsenal got an equaliser in them in these dying minutes? Arshavin and Song pair up in midfield as they continue to press.
United win a throw on the left of the Arsenal goal and are in no hurry to take it, with just five minutes separating them and three points.
Ramsey, already on a booking, jumps into Rooney and the ref has to make a crucial decision. It's a bit late but doesn't look overly malicious and nothing is given.
The visitors respond well as Valencia skips into the box, producing a great one-two with Park before picking out Welbeck, who storms home an emphatic finish.
Looks like the winger whacked his head on the ground as he fell after trying to poke home the ball. He's come round now and having medical attention.
Walcott tries to nudge home a fine cross but gets hurt in the process and looks knocked out after colliding with Lindegaard.
After that raft of changes we're back underway. Welbeck concedes a free-kick for visitors in midfield.
Still a bit confused as to why Chamberlain has been taken off but nevermind, we move on. United are making another change as substitute Rafael is subbed for Ji Sung Park.
Chamberlain goes off for Arshavin to rapturous applause from the home crowd, but they're not happy with Wenger's tactical decision.
Koscielny makes a dubious challenge on Nani to earn himself a booking as things start to get heated.
That goal all started back with Koscielny after that great defending against Rafael. The stopper turned and delivered a great pass upfield and Chamberlain pounced to feed Van Persie, who made no mistake slotting it home.
Rafael breaks for the visitors, feeding Rooney with a well-timed pass. The striker continues the run before trying to play Rafael back in, but Koscielny intervenes.
Just over 20 minutes to go and Arsenal are pressing for the equaliser, exchanging passes just inside the United half.
United win another corner, which Giggs takes quickly. Szczesny charges out again to collect the ball in the box.
The Polish keeper receives treatment on the pitch and doesn't seem any worse for wear seconds later when he leaps to collect Nani's corner.
Szczesny looks injured and there's a worrying moment for Arsenal as Song is forced to hurriedly clear a Welbeck shot.
Chamberlain feeds Van Persie on the wing and he slides in a cross meant for Ramsey, but he can't nod it home.
Valencia hunts down Chamberlain on the left and forces the youngster to put the ball behind for a goal-kick.
Mertesacker tangles with Welbeck in the area and the latter goes down off Szczesny, leaving the German stopper to clear the ball off the line.
Nani tries to find Evra in the box but the flag goes up, then Szczesny saves it anyway. The Frenchman has looked dangerous going forward this afternoon.
So close for Chamberlain, who picks up on a Koscielny pass and beats Lindegaard with his shot but hooks it just wide.
Paul Scholes is warming up and could be called into action for the visitors. United win a goal-kick and Lindegaard hoofs it upfield, looking for Evra.
Replays show Arsenal had a valid handball appeal when Evra appeared to block Ramsey's shot with his arm. Wenger won't be happy with that.
Arsenal win two throws in quick succession as the hosts try to find their way into the game, having come out much brighter this half.
Van Persie looks desperate to attone for his earlier gaffe, sliding a cross in the box which Rosicky, then Ramsey, fails to finish off.
Rafael does well to intercept a Vermaelen pass meant for Chamberlain in midfield. The young Gunners winger is looking threatening on the left.
United win a throw on the left of the Gunners' half, which Nani takes. The ball falls to Valencia at 10 yards and he tries to slice it home but ends up dragging it well wide.
Arsenal are looking more confident, with Chamberlain picking out Ramsey with a well-placed cross, but the Welshman scuffs his shot over the bar.
United win a free-kick in midfield after a Mertesacker foul and they take it quickly, with Carrick feeding Nani on the left.
Walcott and Ramsey pair up with a tidy one-two in midfield before the former attempts to release Van Persie but it's a weak pass and the Dutchman can't latch onto it.
Rosicky charges away for Arsenal down the middle and slides a pass to Van Persie on the edge of the box but the striker's shot is wildly, and uncharacteristically, off target.
Nani breaks away down the left and comes up against Yennaris for the first time, having run rings around Djourou in the first half.
The ball rolls out on the right of the Arsenal half as the Gunners win a throw, and Rosicky hoofs a long ball forward.
Play resumes and it looks like the Dutch ace is ok to carry on. Yennaris gets his first touch and gets a warm reception from the home faithful.
There's a break in play as Van Persie receives some medical attention. The captain gingerly gets to his feet and is walking around. Looked like an impact injury as Valencia landed on him.
Valencia and Van Persie collide and the Arsenal striker is on the floor injured - the last thing Gunners fans want to see.
We're back at the Emirates. Early news on Phil Jones' injury is that it's a twisted ankle, which would be a relief for the visitors.
Almost time to get back underway. Teenage full-back Yennaris is coming on for Djourou, who has struggled in the first half.
Dan Smith tweeted in to say - "Walcott looks sloppy, Chamberlain looks a good choice for England right wing. Untied just deserve the lead at the break."
Akshat Pande thinks Arsenal aren't getting a look-in - "United have been utterly dominant. Rooney has dropped back to the midfield to ensure Arsenal don't break from the back with ease.Smalling and Evans are dealing with the aerial threat way too easily. Apart from a few bursts from Chamberlain, United looking way too secure at back for an away game in North London. Nani has got to make more of his chances when squaring up Djourou. Carrick pulling the strings. Let's keep the foot on the pedal and win handsomely."
Daragh Coulter has dropped us a line to say - "Im following your match report from a ship in the middle of the Atlantic ocean! Hope united do it today!! Predicting a 3-1 united win, with Jones, Hernandez and Rooney on the scoresheet."
Not too much to talk about in that half, with the goal coming in the dying minutes. United have looked the brighter side throughout but can they keep hold of their lead? Get in touch on Twitter @SkySportsRachG or email firstname.lastname@example.org.
We're into the final minute of stoppage time and it looks like United will be ahead going into the break.
Giggs whips in a well-placed cross from the left and Valencia makes no mistake meeting it at the far post, nodding it home with ease. United deservedly take the lead.
Szczesny's goal-kick is not his greatest and United snatch possession straight back as the minutes trickle down this half.
Chamberlain wins the ball from Rafael down the left and makes a break, finding Rosicky, but he drags his long-range effort wide.
Rooney catches an elbow to the face from Song as they both leap to reach the ball and United are awarded a free-kick in midfield.
Nani gets the better of Djourou and, unmarked, tries a shot from an awkward angle, aiming for the far post, but scuffs it across the face of goal.
Carrick blocks a would-be Walcott cross from the right as Arsenal win a throw, which the winger takes.
The Gunners get a chance as Walcott and Ramsey build down the left before the latter tries to pick out Van Persie with a decent cross from the right, but he's beaten to the ball by Smalling.
I'm sorry Rooney, that wasn't a penalty. Song tugged on the striker's arm but he went down a tad too theatrically. Good call from the ref.
United have really upped the tempo in these last 10 minutes and have put the hosts on the back foot. The visitors appeal for a penalty after Rooney is brought down in the box but nothing is given.
Less than 10 minutes to go this half and United are the ones pressing until Song breaks for Arsenal on the counter-attack.
Evra holds off Song to pick out Nani in the box and Szczesny reacts quickly to palm out his close-range shot before Djourou blasts the rebounded ball away.
Rosicky finds Van Persie with a well-weighted pass in the United half but the visiting defence hold firm to close him down.
Nani puts the ball in the box for Evra, who evades the half-asleep Chamberlain to flick on Welbeck, but the striker can't latch onto it.
Djourou lofts in a throw for Arsenal inside their own half but United reclaim the ball, with Rooney feeding Nani down the left.
The veteran midfielder floats it in from far out on the right but it goes straight behind for an Arsenal goal-kick.
Giggs does well to win the ball from Van Persie in the middle of the park and charges off on a superb run before winning a free-kick after some shirt tugging from Vermaelen.
Ramsey makes a well-timed run to meet the ball on the edge of the box but gets a poor first touch and it's another wasted chance.
Welbeck looks dangerous chasing down a pass but Koscielny is right on his tail and he does enough to put off the striker as his shot flies behind.
Rooney makes a solo charge up the length of the pitch then looks for Welbeck on the edge of the box but the home defence intervene.
Rosicky blasts a high ball into the United area but Evans is there to greet it. Walcott and Chamberlain team up in the box soon after but the latter can't keep his shot down.
Giggs tries to squeeze home a shot at the near post after picking up a Valencia ball on the right of the box but Szczesny kneels to collect.
Nani clips it in but Djourou rises and gets his head to it first. United win another corner seconds later and Valencia does the honours this time, but nothing comes of the set piece.
Arsenal have edged the possession so far but there's not much in it, with things looking pretty evenly balanced. Djourou concedes a corner, which Nani steps up to take.
Evans launches a long, diagonal pass into the Arsenal area but Mertesacker gets his head to it to diffuse the threat.
Valencia storms down the right wing and hooks in a cross meant for Welbeck, but Koscielny cuts inside him to hoof it out.
Giggs powers in a cross in the aftermath of United's corner, trying to plant it on Smalling's head, but the Gunners backline manage to clear.
Evra loops a ball into the box, with Valencia lurking near the post, and Vermaelen takes no chances as he heads it behind.
There's a brief lull as the medical team deal with Jones and the teenager is eventually stretchered from the pitch.
Not good news for United as Jones stays on the floor after turning awkwardly. It looks like an ankle problem for the England youngster.
Walcott gives Jones the slip on the left wing, with the United man appearing injured. He powers towards goal but can't pick out Van Persie as Smalling hoofs it clear.
A wayward pass from Djourou misses Chamberlain by yards and rolls out for a United throw. Sloppy from the Arsenal man.
The two teams battle for the ball in midfield, with Arsenal eventually winning possession as Rosicky pounces on the ball.
A clumsy effort from Walcott sees him drive a would-be cross well wide of the box and over the line as a chance goes begging for the Gunners.
Walcott tries his luck with a long-range shot but it lacks power and Lindegaard stoops to make an easy save.
Chamberlain shows great strength to withstand an Evra challenge as Arsenal win a throw near the centre line.
Giggs lofts a long pass towards the Arsenal goal but Djourou is there to clear before the United frontline have a chance to react.
Evra is robbed of the ball by Chamberlain on the left but Rooney is there to claim it back as United patiently probe in midfield.
Van Persie weaves through the United defence to feed Ramsey on the edge of the box and the midfielder slots a shot towards goal, but it's a tame effort and rolls into Lindegaard's waiting gloves.
Lindegaard is there to comfortably snatch an Oxlade-Chamberlain cross to safety as the young winger tries an attack down the left.
The ball rolls back to the Gunners keeper again and he exchanges passes with Song as the hosts mount from deep in their own half.
Van Persie concedes a free-kick in the United half trying to bring down a long Szczesny ball and it's taken quickly by the visitiors.
Song dithers on the ball, allowing Rooney to release Nani, but the Gunners quickly regroup. Giggs tries to pounce on a rogue ball in the area but is beaten to it by a well-timed sliding tackle from Djourou.
Arsenal have taken control in these early minutes, trading passes in their usual style, with Djourou and Song linking up in midfield.
Vermaelen gets away down the left but loses the ball to Valencia. Chamberlain comes back for the Gunners with a pacey run after nicking the ball from Jones but Evans is there to stab the ball clear in the box.
We're off at the Emirates. Szczesny takes an early kick for the Gunners, trying to pick out Koscielny.
Not to drag us all down or anything, but Phill from South Africa is forecasting a goalless draw - "I think we're in for a draw, maybe a frustrating nil-nil to be honest. Too much hype - neither wants to lose." Hope you're wrong Phill!
The teams run out at the Emirates and it's a full house in North London. Thanks for your feedback guys, keep it coming at half-time.
A lot of you seem to think Chamberlain will be the key to United's undoing today. Carol Radford dropped us a line to say - "I think today is the day to unleash the Ox and watch him dominate the midfield, with his fast pace and tricky dribbling he'll cause the Man Utd defenders a headache!"
Just over five minutes to go until kick-off - don't know about you but I'm keeping my fingers crossed for a thriller.
Jimmy London is tuning in all the way from Germany. Think that's our furthest-flung fan so far today. He said - "wanna swap places? I am in germany reading your report!! Enjoy the game. United fan here, lineup looks good. Hoping they bring scholes gets on at some point!"
Ahmed Mohamed is feeling confident the Gunners can get things back on course - "with the verminator and the ox in the team I can see anything but an arsenal win. 2-0 arsenal with chamberlain and RVP."
Sorry to bring it up, Arsenal fans, but the last time these two sides met it ended in an 8-2 thrashing so I'm expecting revenge to be on the Gunners' minds today.
Henrietta Horlicks, from Hemel Hempstead (No, I'm not sure that's their real name either) wrote in to say - "I think the pressure being off the Gunners somewhat may enable them to play a more uninhibited, free flowing style of football, we all know they are capable of and give manyou a right pasting. I predict Arsenal will win 4-3."
Very well, according to Chris Daniels - "We have had the right attitude of recent games, but injuries and other teams mentalities have beaten ours. Today, Alex Chamberlain will make a name for himself! Arsenal to win 3 - 0. Alex Chamberlain to score 2!"
It's a first Premier League start for The Ox - how do you think he'll fare this afternoon with Fergie's top defenders back in action?
Iain Kemble is putting his money on a Wayne Rooney hat-trick -"I think Man utd will just win this one unlike the last game between these two. Arsenal 2 Man utd 3. With Van Persie and Walcott getting the Arsenal goals and Rooney getting all three of the Utd goals. Going to be a very big game today and a game that I can see a shock coming from if Man Utd don't befend to there best."
Dylan Gunner thinks dropping Arshavin to the bench won't do anything to harm Arsenal's chances. He tweeted - "Glad the Ox is starting over Arshavin, rather have enthusiasm than laziness! Come on Arsenal!"
Charlie Richardson thinks Arsenal can overthrow the title chasers - "Pressure's on Man United now with the result at City, but I can't see another 8-2! With Lindergaard in goal and Walcott and Oxlade-Chamberlain playing for Arsenal, I can see an upset here! 2-1 to Arsenal."
The Gunners come into this one on the back of two successive defeats and are fourth points adrift of fourth place - it's not just United needing a win this afternoon.
James Whiting has tweeted to say - "Arsenal need to wake up today or it could be a painful day for the 3rd consecutive week."
A big boost for the hosts this afternoon is that Thomas Vermaelen has shrugged off injury to return to Arsene Wenger's starting XI.
Sir Alex Ferguson's side will be lifted by the return of key defensive duo Phil Jones and Chris Smalling, while the boss has stuck with Lindegaard between the sticks rather than recalling De Gea.
So City beat off Spurs at the Ethiad in the dying seconds to pile the pressure on title rivals Manchester United going into this one.
A quick notes from our friends at Sky Bet - Manchester United (13/8 to win) face Arsenal (also 13/8) this afternoon for the first time since United's incredible 8-2 victory earlier in the season. Manchester United have won seven and lost one of the last nine meetings in all competitions whilst Arsenal have won three of the last five at the Emirates. Wayne Rooney has score six times in his last six appearances against Arsenal, he's 11/2 to score first and 7/1 to score a brace whilst Arsenal captain Robin Van Persie to score first and Arsenal win 2-1 is 35/1.
And the subs... Arsenal: Almunia, Park, Squillaci, Arshavin, Benayoun, Miquel, Yennaris. Man Utd: De Gea, Rafael, Fabio, Scholes, Park, Berbatov, Hernandez.
Arsenal: Szczesny, Djourou, Mertesacker, Koscielny, Vermaelen, Song, Ramsey, Walcott, Rosicky, Oxlade-Chamberlain, Van Persie.
We've got all the team news coming your way in just a sec but first why not drop me a line with your thoughts ahead of the big KO at 4pm? Tweet me @SkySportsRachG or a good old-fashioned email will do - email@example.com.