Arthur Clarke: Would like to be a fly on the wall listening to the conversation between Giroud and Mertesacker in the dressing room right now.

Jonsos RaRaRa: Flamini, champagne positioning, lemonade finishing!

Image source, Reuters

Why, oh why didn't Mathieu Flamini stick his head on this cross just before the break... Clearly he's not an option to stick up front.

Mind you he and Theo Walcott are the only players in the Arsenal XI who have scored against Chelsea...

John Hartson
Former Wales striker on Radio 5 live

"Flamini has to go with his head there, he decided to go with the outside of the right foot and technically that was poor.

"It was Arsenal's best chance and came on the stroke of half-time. Chelsea took a foothold in the game early on and have been comfortable in possession.

"It was a mistake to take off Giroud. The players will be looking at each other wondering where our big centre forward is. 

"Theo Walcott has to take a central role, Joel Campbell has been lively on the right-hand side. Alexis Sanchez is a player who can make a difference."

It's hard to see Arsenal coming back from this, except of course that Chelsea have often been comically poor this season...

Phil McNulty
BBC Sport chief football writer at The Emirates

Chelsea hold the cards in all respects - a goal up and with a man advantage against an Arsenal side struggling to lay a glove on them, bar that late Mathieu Flamini chance.

Per Mertesacker's red card has robbed The Gunners of all rhythm and composure. Manager Arsene Wenger needs to do some fast talking at half-time.

Er, interesting technique from Mathieu Flamini! He's unmarked, six yards out, but instead of planting a header on goal the Frenchman for some reason tried an acrobatic, head-high volley with predictable results.

And that's your half...

An alternative view...

John: Replacing Giroud was best decision in bad situation. Arsenal more likely to win this with pace on break than using a target man

It's 235 miles from my desk to Pete's front room in Romsey but I can just about hear him cursing as Laurent Koscielny sees yellow for a rash kick at Willian.

WHEN WILL THEY LEARN Pete? 

Pete hits us with the big questions...

Diego Costa is unrecognisable from the static, half-hearted striker we saw in blue for the first half of the season. One touch is enough for him to surge past Nacho Monreal and flash in a powerful shot which tests Petr Cech at his near post. Good hands, and then from the corner Branislav Ivanovic has a header off the line!

Image source, PA

A penny for Olivier Giroud's thoughts as he was hauled off...

Another brilliant reverse pass, from Aaron Ramsey on this occasion, finds Theo Walcott - but again he is marginally offside.

Arsenal having a good spell now as they look for a leveller before the break. 

Image source, Reuters

Ben Rabinovich: How can we think about winning the league when we have a mental block when it comes to Chelsea. Not a winning mentality.

Gareth Vaughan: Guus stands for Gets Us Up and Scoring! The man's a footballing savant! Look at the impact he's had on Costa, Fabregas & Mikel.

Daniel Kelly: Arsenal look like it's them who've been down in the bottom half this season, being outdone by Chelsea again. 

Full marks for use of 'savant' Gareth.

John Hartson
Former Wales striker on Radio 5 live

"Arsene Wenger will be sitting down there, he will look at the clock at 35 minutes and think; 'I have made the wrong decision.'

Image source, Getty Images

Arsenal have now been shown more red cards against Chelsea than against any other Premier League opponent - seven.

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What a pass that is! Nacho Monreal dissects the Chelsea defence surgically, a brilliant pass to find Theo Walcott jagging in from the left, but the captain steers his first-time shot just wide. Difficult chance - and in fact he was flagged offside anyway. But encouragement for the hosts as Aaron Ramsey then fluffs a shot wide. 

Alan Green
BBC Radio 5 live

"The cigars are out in the Chelsea defence at the moment."

Image source, Reuters

Chelsea are the only Premier League team this season not to drop any points from winning positions away from home.