The Football Association is examining footage of Leicester's Danny Drinkwater appearing to elbow Watford's Valon Behrami.
The Foxes midfielder clashed with Behrami in the 67th minute of the Hornets' 2-1 Premier League win at Vicarage Road on Saturday.
Referee Neil Swarbrick took no action during the game but the FA, having been alerted to the footage after it ran on social media on Sunday, may act once they discover if the official saw the incident.
If the FA decides there is a case to answer then Drinkwater, who was booked in the game, could face a three-game ban for violent conduct.
Leicester boss Claudio Ranieri remained unconcerned over the incident, ahead of the Foxes' Champions League game with Club Brugge on Tuesday.
He said: "I don't like to speak now about this speculation. I saw the referee was very close to the incident, he doesn't whistle or take any consequences, then I think it's OK."
Drinkwater was initially a major doubt for the game because of a rib injury which forced him out of Gareth Southgate's last England squad.