Phil McNulty
BBC Sport chief football writer at Stamford Bridge

Marcos Alonso did very well to keep out of the earshot and eyeline of manager Antonio Conte as he raged in his technical area, gesturing wildly, at the defender's failure to get on the end of a Victor Moses cross.

And he was then able to make his manager feel much better by scoring Chelsea's goal moments later. This game looks done already.

Victor Moses darts up the right-hand side of the box and hits a tame shot at goal.

Another ball from Fabregas. He's bossing this. 

FYI: There's a bit of contention over Alonso's goal, as it may have been going wide had it not clipped Guzan's leg. Own goal? Maybe. Will it matter? Probably not. Chelsea are in control. 

Steve Claridge
Ex-Leicester striker on BBC Radio 5 Live

Guzan deserves a little more luck there. You can see the pain and disappointment on his face as he sits on his bottom there. 

This is a bubbly, upbeat, "we are going to win the league" performance from Chelsea tonight. 

Another wonderful move from Chelsea. A lovely flick from Eden Hazard falls to Victor Moses but he can only cut his shot across the face of Brad Guzan's goal. 

I think there was a wolf-whistle from the crowd to congratulate that move...

Image source, AFP

Kevin Samuelson: Conte must win the award for most passionate pitch side displays this season, the guy is brilliant to watch.

Bennybwalya: This will be the easiest victory ever... I forsee a 5-0 win for Blues.

Steven Thelwell: As a Spurs fan with Costa as fantasy football captain should I be cheering the goal? #conflictofinterests 

Chelsea are building up patiently. 

David Luiz sends a long ball cross-field to Victor Moses. They work it across midfield before Fabregas feeds into the box, but he's over hit it. 

Cesc looks in great nick tonight. 

Cesc Fabregas earns Chelsea a free-kick on the right-hand side of the box and Boro have 10 men back.

Alvaro Negredo clears by booting it down field. 

Phil McNulty
BBC Sport chief football writer at Stamford Bridge

Middlesbrough were clinging on by their fingernails from the first whistle and it could not last forever.

Chelsea simply ramped up the pressure and doomed Boro had to crack eventually. Much technical area joy from Antonio Conte - and his fellow Italian and 2010 Premier League and FA Cup double winner here Carlo Ancelotti looks impressed as he watches from the stand at Stamford Bridge.

Image source, Rex Features

Now they're singing at Stamford Bridge. The goal has settled Chelsea's nerves and raised the voices of the Blues faithful. 

Boro have got an even bigger hill to climb now.

They're not sitting back, though. Marten de Roon tries to turn and shoot but his effort is blocked by Gary Cahill. 

Steve Claridge
Ex-Leicester striker on BBC Radio 5 Live

That is the same ball that has caused Middlesbrough problems all evening. 

A really good finish and the type of goal - that chip and control - that has been coming. This time they made it count.

Steve Claridge
Ex-Leicester striker on BBC Radio 5 Live

It looks to me like that was a wonderful bit of "gamesmanship", if you like, just to usher Diego Costa out. 

A strong challenge but does he get the ball? No.... 

Image source, AFP

Diego Costa is in the back of the net...but without the ball.

A sensational cross lands at the feet of Eden Hazard. He darts forward and finds an on-rushing Costa dead centre in the box, but he can't scramble home because George Friend has got in the way.

Chelsea earn their first corner now. David Luiz and Gary Cahill are lurking but Cesc Fabregas can't find either of them.

The Blues build-up the attack again, Costa lays off to Hazard, who lays off to Fabregas, who takes a punt from distance but it goes wide of the post. 

Ol' Cesc probably should have done better with that. 

David Luiz lines up to take the free-kick. He gets a pointy toe underneath it and it goes over Brad Guzan's bar. 

West Brom manager Tony Pulis is in the crowd at Stamford Bridge tonight, assessing the Blues before his side face them on Friday. 

At least I think it's him. He's not wearing a cap nor a track suit. In fact, he's looking pretty dapper. 

On the pitch, Chelsea earn a free-kick about 25-yards out after Fabio brings down Diego Costa.