We're not sure why, but Diego Costa really is the angriest man alive!
It's safe to say Diego Costa is our favourite pantomime villain in the Premier League - he's angry, he's aggressive, the sort of guy who would kick you for fun.
The Spanish striker had a big altercation in the first half with Laurent Koscielny. Firstly, Costa managed to push him in the face, not once but twice, and then, after he bundled the striker over, surprise, surprise, Costa reacts and pushes him over.
Then Brazilian defender Gabriel gets involved and it kicks off again, with Gabriel and Costa both getting yellow cards before the Arsenal man got sent off for a silly show of petulance.
With Costa getting every Arsenal fan raging, and neutrals torn between hatred and admiration, Twitter went a bit mad, and here are some of the best tweets:
Top Corner (@HITCtopcorner) September 19, 2015
Diego Costa is 100% the type of bloke who would start a fight, then either run off or get his mates to hold him back. #CFC— Top Corner (@HITCtopcorner) September 19, 2015
Unreal Diego Costa helping Koscielny protect his eyes from the burning sun. this is fair play. This is football. pic.twitter.com/RuGT2diVEr— Catalan Cafu (@ElAficionadofcb) September 19, 2015
Diego Costa coming off, Arsene Wenger waiting for him like... pic.twitter.com/4yRpFhaOfL— TheSPORTbible (@TSBible) September 19, 2015
Diego Costa would start a fight with his own reflection in the mirror.— Footy Humour (@FootyHumour) September 19, 2015