West Ham boss Alan Curbishley has accused Bristol Rovers' Joe Jacobson of "lashing out" at Kieron Dyer in a tackle that broke the midfielder's leg.
Dyer receives treatment before being stretchered off
Dyer, 28, suffered a double fracture to his lower leg during West Ham's 2-1 Carling Cup victory on Tuesday.
Curbishley said: "We're devastated for Kieron. I can't put it into words. The game was just immaterial after that.
"The player has got to be disappointed with his tackle. As far as I could see, he lashed out after losing the ball."
A club statement said: "Kieron was stretchered off the pitch and rushed to hospital where it was confirmed he had fractured both the tibia and fibula of his right leg.
"It is too early to say how long he will be out for as this will become clearer once the first stage of surgery is completed."
Joe is not that type of player and we're not that type of football club
Rovers boss Paul Trollope disagreed with Curbishley, saying he thought Jacobson's tackle was a foul but disputed that there was any intent to hurt Dyer.
"Joe swung his leg back to try and get the ball and that was it," he said.
"The story coming out from the other camp saying it was a malicious tackle and he's gone to do him are really wide of the mark.
"He is not that type of player and we're not that type of football club.
"Our thoughts are with Kieron Dyer - you don't wish that on anyone."
But Curbishley added: "The players could see what happened and that's why they were so angry.
"Everyone in the dressing-room is really flat but we've got to get over this.
"The game was irrelevant after Kieron's injury. I'm really down because he was looking sharp out there, playing in his favourite position in the middle of the park."
West Ham won the game 2-1 to go through to the third round, thanks to striker Craig Bellamy's first goals for the club.