Lucas Perez says "false information" implied he refused to play in West Ham's 3-1 win at Everton on Sunday, reports BBC Sport.
The Spanish striker, who started the Premier League game on the bench, had looked set to replace the injured Marko Arnautovic, but boss Manuel Pellegrini opted for Michail Antonio instead.
"I have never ever refused to warm up in my whole career, let alone play a match," he tweeted.
Perez explained that West Ham's substitutes take it in turns to do warm-up routines of three to five minutes during a game, and that he had not been warming up when Arnautovic got injured.
"In the moment Marko got injured, I was on the bench after warming up," he added.
"The coach [Pellegrini] called me to go out and play - however, having realised that it was faster to substitute Antonio in, who at that moment was warming up, he changed his decision."
The striker said: "The images that have been misinterpreted correspond to a talk with the goalkeeper's coach, in which I never refused to warm up and explained what happened."