New season, new manager but it was the same old Diego Costa.
The Chelsea striker was his usual combative self as he was booked for arguing with referee Anthony Taylor, clashed angrily with team-mate Nemanja Matic and then could have seen red for a crude, late challenge on West Ham goalkeeper Adrian.
Eden Hazard put Chelsea ahead in the 47th minute by scoring from the penalty spot after Cesar Azpilicueta went down under a clumsy challenge by Michail Antonio.
James Collins equalised with a wicked left-footed half-volley in the 77th minute but Costa had the last word with an 89th-minute strike.