West Ham manager Sam Allardyce criticised Kevin Nolan after holding the club captain responsible for the 2-1 New Year's Day defeat at Fulham.
Nolan's captaincy is to be reviewed by Allardyce after he was sent off for kicking Fernando Amorebieta in the Barclays Premier League relegation showdown at Craven Cottage.
The dismissal came two minutes before half-time with the match finely poised at 1-1.
It was his second red card in less than four weeks after a lunge at Jordan Henderson in the 4-1 defeat at Liverpool on December 7 resulted in the same punishment.
Dimitar Berbatov produced the second-half winner that saw Fulham climb out of the relegation zone and left Allardyce questioning Nolan's state of mind.
"After a great start we looked like we could get another one, and go on and test this back four of Fulham's. But when you have a man sent off it gets very difficult indeed," he said.
"So he's responsible for us probably losing the game more than anything else, there's no doubt about that.
"I don't understand it because this indiscretion comes straight after what happened at Liverpool.
"So I'm going to have to find out what's wrong with him, there's something wrong with his mentality at the minute.
"Because at his age and his experience, he's a player I've known for many years, I haven't seen this type of reaction or this type of situation that he's put himself into.
"The responsibility of the player is to play the game to the best he possibly can, and to go out and be disciplined, apply his talents in the correct manner within the laws of the game - not to lose your head, and not to do anything silly.
"I just don't quite understand where he's lost his cool and why it's happened."
West Ham led through Mohamed Diame's seventh-minute strike but Steven Sidwell equalised before Nolan's dismissal enabled Fulham to gain the initiative and pepper their opponents with shots until Berbatov finally struck.
The victory was an immediate response to Saturday's harrowing 6-0 rout at Hull and head coach Rene Meulensteen was impressed by the way his players reacted to the red card.
"The sending-off helped us but we still had to be calm and attack with quality," said Meulensteen.
"You see teams struggle against 10 men all the time, but I told the players to attack, but keep that quality.
"We definitely deserved the result because we had plenty of chances."