Alex Ferguson has vowed to deal with his defender Rio Ferdinand after he refused to wear a "Kick Racism Out of Football" t-shirt before Manchester United's 4-2 victory over Stoke at Old Trafford.
Ferdinand was taking part in a protest by certain black players, led by Reading striker Jason Roberts who claimed that the anti-racism movement was not doing enough to deal with the high-profile problem.
The 33-year-old is also thought to be angry that Chelsea defender John Terry was only given a four-match ban after being found guilty of racially abusing Ferdinand's brother Anton during a match against QPR last year.
United boss Ferguson was highly critical of Roberts in a press conference on Friday and was stunned when Ferdinand followed his example in refusing to wear the t-shirts which were worn by all players from both clubs, with the exception of Stoke forward Kenwyne Jones.
"I am disappointed because I said yesterday that the players would be wearing it," Ferguson said.
"We did that in support of the PFA. Every player in the country should have adhered to that. He goes and lets us down. We will deal with it. Don't worry about that.
"I'm very disappointed. You support the PFA, the request from them and all our players made that. He's let us down so we will deal with it."
Jones' refusal to don the t-shirt will generate far fewer headlines than Ferdinand's actions and his club manager, Tony Pulis, was far more relaxed about his player's behaviour.
"I think players are given the opportunity and chance to decide and that's what we've got in this country," said Pulis. "Do I agree with it? That's my opinion.
"Let me just say, in this country, never mind what people say or don't say, they have the right to say yes or no.
"In a lot of countries, you don't have that right, in this country you do. You have the right to do what you want to do, the right to stand up and do it or not.
"When we see incidents like we did in Serbia and the incidents that have taken the headlines, this is the greatest country in the world for multi-culturism."
Meanwhile, once the game kicked off, Wayne Rooney gifted Stoke the lead with an own goal before scoring twice, with further efforts from Robin van Persie and Danny Welbeck completing United's scoring while Michael Kightly claimed a second for the visitors.
Rooney, who had not scored a club goal this season until the win, now has 200 goals for Everton and United over the last decade and is looking forward to a profitable pairing with van Persie.
"As long as I'm playing well it doesn't concern me if I'm not scoring goals," said Rooney. "But it is nice to get off the mark this season for United.
"I didn't know I'd reached that landmark until I was told after the match but obviously I'm delighted to have achieved that. I'm sure me and Robin will get better and better the more games we play together.
"It was a great ball in from Robin for the first goal. We are getting more of an understanding. We are both pleased with the way it is going. We have great attacking options. It is down to the manager to pick us."
United now have 21 goals in eight Premier League games and Ferguson added: "For Wayne and Danny getting off the mark for the first time this season helps. Wayne will get better with games, so will van Persie.
"They give us that flexible movement we have up front. Robin ended up wide left and put a great cross in, Wayne had a fantastic header.
"That kind of movement does bother teams and I am glad they have started to gel quite well.
"Robin, as we know, didn't have many pre-season games and Wayne was out with his injury. The more games Wayne gets, the better he will become."