Phil McNulty
BBC Sport chief football writer

Image source, Getty Images

"Excellent first 45 minutes from two teams playing as if their hopes of a trophy rest entirely on the FA Cup. Arsenal are playing with ambition, with Alexis Sanchez a class act, while Angel Di Maria is making inroads down the flanks, as emphasised by his cross for Wayne Rooney's header. Enthralling second half in prospect."

Wonderful game Well done one and all.

If you've missed any of the key moments in this match, you can watch them again via the highlights tab throughout the evening. The Arsenal goal is in there now, with Rooney's to follow any minute.

Phil Neville
BBC Radio 5 live

"It's a really tense atmosphere inside the stadium. Both sides are really committed here and want to go through in this tie."

I was at Wembley last May when Santi Cazorla delivered a peach of a free-kick into the top corner of the Hull net, he looks up to take another free-kick form a similar range but this time he can't beat David De Gea in the United net.

Chances at either end as first Alexis Sanchez beats two men but can't shoot, and then Marouane Fellaini hits one at Wojciech Szczesny after a nervous clearance form the Pole.

Image source, Reuters

Angel Di Maria in again down that right, he latches on to another 'long ball' from Antonio Valencia and this time does shoot. Not the most powerful drive but a good save from Wojciech Szczesny all the same.

Phil Neville
BBC Radio 5 live

"If Angel Di Maria had taken that fantastic ball from Wayne Rooney on his right foot, he'd have been in on goal there."

What a ball! Wayne Rooney puts it on to Angel Di Maria's foot with a gem of a clip over the top. Di Maria needs to smash it first time though and he doesn't want to. Chance has gone.

First half almost gone. It's sailed by.

Danny Murphy
BBC One

"The game has calmed down a bit which is to be expected after that frantic 10 minute spell. But I think we will get another goal."

Image source, AP

Alexis Sanchez is a joy to watch, he really is. Signing of the season? He leaves two United men on their backsides with a jagging run. Even Mesut Ozil is putting tackles in, it's a committed performance from all 22 men thus far.

Mark Tomlinson: Look what happens when Rooney is actually played in his natural and best position! Great header and goal!

Phil Neville
BBC Radio 5 live

"Ashley Young is hugging that left touchline. As soon as he gets that ball out wide, he's driving on and looking to get past Hector Bellerin and be really positive."

Alex in Cardiff: Chris Smalling caught ball watching when he should have realised Valencia had moved across and covered his position. Has never, and will never, be Manchester United quality.

Paul in Manchester: That goal shows why Chris Smalling is not good enough. Didn't have the intelligence to stay out in the full back position.

Sloppy from Angel Di Maria to take too long in midfield, he's stripped of the ball and then pulls down Alexis Sanchez. Ander Herrera is booked in fact, it was a sandwich challenge.

Jason: Are we finally seeing the Di Maria we've waited for all season? His passing has been sublime today!

Wayne Rooney has scored in his last three FA Cup games against Arsenal - he's never won the trophy though. You may be surprised to hear that. I was.

Will he add it, will he lift it, this year?

Daniel Woodley: Two fantastic goals so far. End-to-end game and not one for defences

That's why you've been dropped son! Wojciech Szczesny, seemingly relegated to Arsenal's Cup keeper, makes a total hash of collecting a cross and is very lucky that he doesn't drop it at the feet of Wayne Rooney for a tap-in. There's no time to breathe in the game, gripping stuff.

David De Gea with another save for his 2014-15 collection, getting down well to push out a header form Danny Welbeck. More good work from Alex Oxlade-Chamberlain down the right to pick him out.

Danny Murphy
BBC One

Image source, EPA

"When Wayne Rooney plays as a striker you know he is going to get goals. It's a great response from Manchester United. It's not the first ball Di Maria has put in from the right-hand side. It's whipped in with pace and what a header."