The pundits are arguing now. That red card has riled everyone. 

Jermaine Jenas
Former England midfielder on BBC Radio 5 live

Chelsea have not been at their best, that's probably because Manchester United have nullified them by breaking up their rhythm with little fouls.

Antonio Conte will be looking at how to change things. It is screaming for someone like Cesc Fabregas to come on. More creativity is needed.

We know what Rio Ferdinand thinks about the sending off, have a look at this and judge for yourself...  

Paul from Surrey

James, a Chelsea fan

Richard in Scunthorpe

There goes the whistle. Pick the bones out of that little lot. 

How's that FA 'respect' campaign going?

Image source, AFP

The chances of this game going to penalties increased exponentially with that red card of course. We haven't had a chance since Ander Herrera walked. 

Not surprising to see a former Manchester United hero questioning Michael Oliver's performance...

Some app users may have to click the link to see this Tweet.

Poor old Marcus Rashford needs a wi-fi signal to communicate with the rest of his team now, he has an ocean of space between the men in red and himself.

Phil Jones whacks a ball over his head and asks him to chase it. 

Phil McNulty
BBC Sport chief football writer at Stamford Bridge

It was coming. This FA Cup quarter-final has been right on the edge and it has boiled right over - and that includes the two managers.

We've had a sending off and now Antonio Conte and Jose Mourinho have to be separated on the touchline.

It's a tough job for referee Michael Oliver, who was surrounded by Manchester United players after showing a second yellow card to Ander Herrera.

Gary Cahill trips Marcus Rashford, no booking, and Jose Mourinho and the United players have justification to ask why...

Here are a couple of gems that Ander Herrera won't want to hearing while he takes his early bath.

He has been responsible for two of Manchester United's three red cards this season. 

The Spain midfielder is the first Red Devils player to be sent off twice in a season since Nemanja Vidic in 2013-14. He still wake sup in cold sweats thinking about Fernando Torres.

Martin Keown
Former Arsenal defender on BBC One

I think there is a healthy respect between the two managers. they are both winners. They want the same thing. I can't help but feel the red card has spoiled the game. I would have loved to see it played out with 11 on each side.

The action on the touchline trumps that on the pitch at the moment.

Manchester United are down to 10 men, that's the headline.

Image source, AP

Ref Michael Oliver comes to the sidelines and has a word with Antonio Conte and Jose Mourinho.

BEHAVE.

Eden Hazard has been fouled four times, and they were all similar too. If anything the one Ander Herrera was booked for first was the softest one.

Jose Mourinho and Antonio Conte are having more words - someone else is going off before the end of play as Victor Moses shoots over the top. 

Dan Walker and Ruud Gullit were doing a Facebook Live chat which was somewhat interrupted when Ander Herrera got sent of...

Jermaine Jenas
Former England midfielder on BBC Radio 5 live

I think Ander Herrera has been silly. He can complain all he likes but it is another challenge on Eden Hazard when referee Michael Oliver has just called over another player to tell them to calm it down on Hazard. 

You're already on a yellow card - why are you going in there? It is persistent fouling, not dangerous, but he has warned them. He is in his right to send him off. 

When one player is being targeted, you need to protect that player.

David de Gea is now in a heap in the goalmouth after a challenge from Diego Costa. Referee Michael Oliver is under the cosh here.

There wasn't much in that. 

Martin Keown
Former Arsenal defender on BBC One

I think Michael Oliver has just run out of patience. It is one foul after another. I have sympathy. You can't keep making fouls. Herrera is on a yellow. He needs to be sensible.