The Argentine looks set for a spell on the sidelines.
Manchester City lead Everton 1-0 at the break, after a poor decision from Andre Marriner to give a penalty to Manchester City for a soft collision between James Milner and Phil Jagielka - Yaya Toure dispatching the penalty.
Toure was taking the spot-kick because their usual man for the job, Sergio Aguero, had come off injured.
The Argentine has been in terrific form this season, scoring 19 goals in 22 appearances. But despite a big game in the Champions League against Roma coming up Manuel Pellegrini decided to keep Aguero in the starting XI.
After three minutes he was regretting that decision.
Aguero over-extended in a challenge with former team-mate Gareth Barry, and ended up lying on the floor in agony. The early diagnosis was a knee problem but it is apparently now reported as a thigh issue.
Either way it clearly had the player worried. He was in tears before being escorted from the pitch, without the aid of a stretcher.
Title rivals and Roma will secretly hope it is serious enough for him to miss upcoming fixtures, but most neutral fans will certainly hope he is back in action sooner rather than later.