Stoke - Diego Costa faces the risk of disciplinary action after a steward claimed he deliberately trod on his foot during Chelsea's 1-0 defeat at Stoke City.
The controversy-prone striker's conduct fell under the spotlight last weekend after he escaped censure for kicking out at Liverpool defender Martin Skrtel during his side's 3-1 home defeat.
But Saturday's incident looked far more innocuous, with Costa appearing to make fleeting contact with the steward as he ran over to pick up the ball for a throw-in as Chelsea chased an equaliser at the Britannia Stadium.
Stoke confirmed that a member of their security staff had reported Costa to match referee Anthony Taylor, but a Chelsea spokesman said: "This claim is utter nonsense."
Taylor will nonetheless be obliged to mention the complaint in his report even if, as appears likely, the FA see no grounds for taking further disciplinary action.
Chelsea were condemned to a third consecutive league defeat by Marko Arnautovic's 53rd-minute goal, which left the reigning champions in 16th place in the Premier League table.
Manager Jose Mourinho was not present as he served a one-match stadium ban for berating the referee during Chelsea's recent 2-1 loss at West Ham United.