Sergio Aguero is facing a potential three-match ban after throwing an elbow at Winston Reid on Sunday - and could miss the Manchester derby.
The striker caught West Ham's central defender late on during Manchester City's 3-1 win, sealed by a Raheem Sterling double and Fernandinho header.
Referee Andre Marriner was close by but did not give a foul and it appeared on Sunday night that he was unaware of any violent conduct.
The Football Association are likely to look at retrospective punishment should Marriner claim he did not see the incident.
Reid was left unable to speak properly in the dressing room afterwards, with Mark Noble saying: 'I know he couldn't talk. He said it was because he had got something in the throat.'
A suspension would see Aguero miss the titanic clash with Jose Mourinho's United at Old Trafford on September 10, another Premier League game against Bournemouth before a trip to Swansea.
'I didn't see it, so I cannot comment,' City manager Pep Guardiola said.
'Hopefully nothing happens. If it happens, we accept and adapt. If we lose him, we lose him. We are (still) going to play with 11.'
Sportsmail columnist Jamie Redknapp said afterwards that Chelsea's Diego Costa would be held up as an example had he performed similar.
'If that's Costa I've no doubt there'd be some retrospective banning but he's never been sent off in 212 games for Manchester City,' Redknapp said. 'Is that really in his nature? I'd have to say no.
'How can (Marriner) not see it? I don't think anyone wants to see a player like Sergio Aguero banned. Of course we don't but it doesn't look good.'