Henrikh Mkhitaryan is the sacrificial lamb as Marouane Fellaini comes on. That will really calm things down. 

You can protest all you like, and he really, really likes, but Ander Herrera is off! He's already been booked and trips Eden Hazard once again.

It wasn't a dangerous tackle, but it's a foul and a booking most weeks. He is shown a second yellow card but doesn't like it, giving referee Michael Oliver a discussion on his way off.

Jose Mourinho laughs. 

Martin Keown
Former Arsenal defender on BBC One

It gets very difficult for Manchester United in that midfield. There are so many willing runners. They are spread out like a flower, the Chelsea team.

Eden Hazard gets a kick in the back of the shins again, actually that was more of a push. Phil Jones into him that time. He's just doing his job to be fair.

Antonio Conte and Jose Mourinho disagree. Loudly. 

A reminder that we could go to extra time and/or penalties tonight. I would say the chances are good. Bad news for my dad, who will be furious to put on BBC One for the 10 o'clock news and find this rubbish on instead. 

I'll get the blame for that next time I speak to him.

David de Gea has made some important saves already, including this one from Gary Cahill...  

Chelsea have shaded possession, holding on to 56% of the ball, as they have grown into this tie.

They are also leading in the shots column, popping six attempts at the United goal. Only two have come the other way and neither was on target.

Interestingly, all six of Chelsea's shots have come from different players - Cahill, Kante, Moses, Hazard, Matic and Costa.

Image source, Opta

Victor Moses (number 15) has had an absolute shocker there...

Martin Keown
Former Arsenal defender on BBC One

He snatched at it. Phil Jones makes the tackle and suddenly Hazard is on it. But it is a wild finish. He looks like the one player who could make the difference.

Superb again from Eden Hazard, so direct and dynamic as he skips through a gap, beats Phil Jones and shoots on his left foot. It's wild and wide but the threat was clear. 

Phil McNulty
BBC Sport chief football writer at Stamford Bridge

Chelsea's supporters fire some fruity abuse at Jose Mourinho after he complains about what he saw as an Eden Hazard dive. He raises three fingers & mouths at the fans. Three titles?  

Jose Mourinho shows three fingers, one for each Premier League title, to some Chelsea fans who are presumably giving him a bit of stick. Cue the faux outrage. 

Jermaine Jenas
Former England midfielder on BBC Radio 5 live

It has been fascinating from a tactical point of view. 

I've been very impressed by Manchester United, despite Chelsea having the best two chances - how aggressive they have been and their reading of the second ball, particularly Phil Jones. 

Eden Hazard likes to pick the loose balls up and Jones is stopping him. It is set up to be a brilliant game.

It's another brilliant run from Eden Hazard to weave past two or three Manchester United players but Paul Pogba extends the go-go-gadget legs to slide in and take the ball cleanly. Great tackle. 

This had everything except for the goal at the end of it, thanks to a flying save from David de Gea...

The ball has been under control for maybe 35% of this game so far. It's very much up-and-at-em stuff. 

Phil McNulty
BBC Sport chief football writer at Stamford Bridge

Eden Hazard has quickly emerged as Chelsea's biggest threat - and Manchester United are happy to try the heavy-handed stuff to stop him. A blatant obstruction by the increasingly combative Ander Herrera then a trademark clumsy foul by Phil Jones.

Nemanja Matic sails a shot way over the bar from a mile out as United then attack for the first time in a few minutes, Antonio Valencia sends in a dangerous cross, Victor Moses slips at the far post but he gets away with it.

Ruud Gullit
Former Chelsea manager and BBC One

A high quality game. United are trying to press high. They are looking to allow Cahill plenty of the ball as he is the one who makes mistakes more often.

First 10 minutes not good, second 10 minutes very good. It's being played at an extreme tempo, like an LP on the wrong setting.

Phil Jones is the latest man to foul Eden Hazard, who is getting the full treatment.