Several contenders: Silva, Fernandinho, Dzeko, in a team of impressive performers.
But it has to be Yaya. He has played a huge part in the position we're in at present.
The more forward he is played, the better, and not further back in a more defensive midfield role, and he has proved that with his goal tally this season.
He has spurts of brilliance, as opposed to more frequent bouts of a much lesser quality. Once he gets the ball, one gets an assuring feeling that he's going to do something delightful with it, which is usually the case. Tough challenges don't seem to faze him, and it's like he has carte blanche over time and space during his bursts of energy when he has possession, and imo nobody else in the league has that uncanny ability and demeanour, which is often interpreted as laziness but I'd prefer to call it effortlessness.
True legend.