The Diego Costa discussion will go on and on - at least we are not talking (much) about a handshake anymore, hey?

But this is where I have to leave you...

For a developing match report go here.

And get the rest of the fall-out from Stamford Bridge, plus all the team news and build-up for all the 15:00 BST games here.

Danny Mills
Former player on Final Score

"The problem is the ref will now hide behind the letter of the law. He will say, "He raised his arm". Raising your arm is not a red card offence. 

"There was more than enough to send Costa off in that situation. Referees seem very reluctant to actually talk to players these days". 

Danny Mills
Speaking on Final Score

"The inconsistency of the referee is ridiculous. Is it violent conduct? No. Is it endangering a player? No. It's definitely not a red card". 

Garth Crooks
Final Score

"Every so often I think you need a referee in a situation who is sensible, and treats the players like men.

"If no-one had been sent off in that clash between Costa and Gabriel, no-one would have screamed. 

"The only man who was interested in sending someone off was the official. Don't look for excuses to send players off. Just do you job and try and keep it 11 v 11. 

"Mike Dean is a really good referee but he has one fault - he wants to be the star too often. It's not about you, Mike. People pay good money to see good football. It's not about you behaving like a schoolteacher."

Pat Nevin
BBC Radio 5 live

"It was a great game in the first half, but it all changed in that moment between Gabriel and Costa. Have a good look at every camera angle, and the most important angle is the one where you can see how the referee say a kick out from Gabriel. If he did do it, Gabriel had to go - full stop."

So, Chelsea return to winning ways... Diego Costa was not on the scoresheet but you can bet your bottom dollar he will what everyone will be talking about after this match. Arsenal boss Arsene Wenger will surely have an opinion on the part the Blues striker played in Gabriel's sending off before half-time.

No handshakes between the managers at full-time. Arsene Wenger is straight off down the tunnel, while Jose Mourinho celebrates with his players.

 John Obi Mikel came on for Cesc Fabregas in the aftermath of Chelsea's second goal and has a think about having a shot after picking up the ball inside the Arsenal half. That would have been a collectors' item. In the end he thought better of it and passed it to a Blues team-mate.

Pat Nevin
BBC Radio 5 live

"There are so many positives for Chelsea. They haven't played brilliantly today but they have managed to beat their great rivals Arsenal. And Hazard finally gets a goal, and he has played with quality. 

"It's been a great game for Chelsea and now they can build from here. And you suspect that they will.

"Do you think there will be a handshake between the managers at the end?"

Arsenal's nine men have still not given up completely, although you could hardly blame them if they did.

Instead, Theo Walcott's nod down in the area finds an onrushing Aaron Ramsey but Asmir Begovic is there to deny the Gunners what would surely only have been a consolation.

Every time an Arsenal player commits a foul, the Chelsea fans bellow "off, off, off". Mike Dean is keeping his cards in his pocket at the moment, though, and Chelsea are still keeping hold of the ball.

Pat Nevin
BBC Radio 5 live

"Up until the second sending off I still thought there was a chance for Arsenal in this. But Arsenal should still take chances - why not? So they end up losing 2-0, so what?"

You can listen to live commentary of this fixture via the Live Coverage tab at the top of this page.

Chelsea's dominance continues. 

Laurent Koscielny trips Eden Hazard on the edge of the Arsenal box. The Belgian takes the free-kick himself, but his shot hits the top of the wall and flies over.

Arsenal cannot get a touch at the moment.

Pat Nevin
BBC Radio 5 live

Image source, EPA

"Costa had been walking a tightrope. Just before he was substituted he took another risk, tangling with Oxlade-Chamberlain. And now Mourinho has removed him."

Chelsea are playing keep-ball in their own half as we enter the last five minutes of the 90.