Chelsea defender David Luiz has reportedly told team-mates that he was laughing at a comment shouted at him by a Manchester United fan when Rafael was sent off at Old Trafford on Sunday.
Rafael kicked out at Luiz in the 89th minute, and while referee Howard Webb was producing the red card the Chelsea defender was caught on camera smiling while laid on the floor, supposedly in agony.
That led to widespread condemnation of his actions for alleged gamesmanship, with United boss Sir Alex Ferguson claiming that Webb had been duped by the Brazilian defender.
Sir Alez said: "He [Rafael] was elbowed. He retaliated. That always happens, the player that retaliates gets the heavier penalty. It was quite clear Luiz has elbowed him twice. The referee has been bought by the fact Luiz has rolled about.
"The referee hasn't even seen it at all. He has gone with the fact Luiz has rolled around on the floor and that has convinced him it is a red card. You see that a lot with European, foreign players and South Americans.
"Certainly the refereeing decisions went against us. They surrounded the referee all day, four or five players all the time. I think that affected the referee."
A report in the Daily Telegraph on Tuesday claims that Luiz insists he was giggling at a jibe from a United fan about his resemblance to Sideshow Bob, a character from television show The Simpsons. Luiz has long been compared to him due to his big hair and his sometimes calamitous career in England.
Chelsea won the game at Old Trafford 1-0.