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Reports pre-game suggested that Costa, who would have likely learned of his omission 60 minutes before kickoff, refused to warm up with his Chelsea teammates.
When it became apparent in the 92nd minute that he wasn't going to be used as a substitute, Costa took off his bib and threw it in the direction of Mourinho.
Midfielder John Obi Mikel found the incident quite amusing.
Obi Mikel loved It 😂😂😂😂 #DiegoCosta pic.twitter.com/I9Wb7kFAia
— Odd Fu†ure (@YusefA10) November 29, 2015Mourinho attempted to brush the incident off during a post-match interview.