So, this match was decided by a Diego-Costa-sends-a-player-off incident with Gabriel getting a ridiculous red card and Chelsea taking advantage to run-out 2-0 winners over Arsenal.
A match that was pretty cagey for 40-odd minutes turned on its head when Costa induced a red card for Gabriel, with referee Mike Dean making a decision he will rue, or not, for some time.
Costa took a couple of potshots at Laurent Koscielny, trying to rile the Arsenal defender, and when that wasn't successful, he barged into the Frenchman, which brought Gabriel into play.
A war of words ensued and after Dean gave both players yellow cards, Costa made the most of a slight movement of Gabriel's foot, which led to the referee showing a straight red card.
Having to play with 11 men against the champions is hard enough, so playing with ten proved to be even more difficult – it would become nine a little later as well, with Santi Cazorla sent off by the wonderfully-gifted referee -- with Kurt Zouma and Eden Hazard scoring in the second half to help Chelsea to victory.