Manchester City forward Sergio Aguero could face disciplinary action after appearing to elbow West Ham's Winston Reid.
The incident occurred in the 76th minute of Manchester City's 3-1 win at the Etihad Stadium and Reid had to be substituted after receiving treatment.
The duo challenged for a long clearance from Hammers goalkeeper Adrian and Aguero swung his elbow towards Reid, apparently catching the side of his head or neck.
Sky Sports pundit Niall Quinn observed: "He has been a bit naughty, Aguero here. He has swung out and he is a lucky boy. If the referee sees that, he is in big trouble."
Reid did not attempt to continue and was clutching his neck as he left the pitch, to be replaced by Jonathan Calleri.
Manchester City will now face a nervous wait to find out if referee Andre Marriner witnessed the incident and if, as seems likely, he did not, whether the FA decides to charge Aguero with violent conduct, which could lead to a three-match ban.
City's first game after the international break is a local derby at Old Trafford against Manchester United, both teams having won their first three Premier League games of the season.
Asked about the Aguero-Reid clash, Manchester City manager Pep Guardiola was non-committal, telling Sky Sports: "I did not see anything.
"I will see what you are talking about on TV and, after that, we are going to see."