Arsenal have now been overtaken at the top of the table as they drop to third place after Diego Costa's first-half strike earned Chelsea victory and a league double on Sunday evening.
Arsenal had Per Mertesacker sent off in the first half after a tackle on Costa after Chelsea broke forward through Willian. The Brazilian sent a good pass in behind Mertesacker which saw him sliding in on Costa as last man to receive a red card from Mark Clattenburg.
Five minutes later Costa took advantage of his side’s advantage in numbers and put chelsea ahead when he sent home Branislav Ivanovic's low cross.
The victory gives Chelsea some respite as they now come up to 28 points and 13th position.
Wenger got destabilized as he responded to the dismissal by taking off in-form striker Olivier Giroud for Gabriel Paulista, much to the disappointment of the French forward and the Emirates crowd, which he might have realized too little too late that it was a rush decision.