The Chelsea defender David Luiz has told friends that he was laughing at a Manchester United supporter who berated him as "Sideshow Bob", the character from The Simpsons to whom he bears a resemblance, in the moments after he was fouled by Rafael da Silva on Sunday at Old Trafford.

Luiz, 26, has been widely criticised for his reaction to the foul, for which Rafael was sent off, after he was caught on camera smirking as he lay on the ground holding his right ankle. Sir Alex Ferguson described his tumble to the ground after the kick, a clear foul nonetheless, as a "dying swan" act.

Luiz has maintained in private that he was responding to a supporter in the area where the Stretford End meets the Sir Alex Ferguson stand who shouted at him. It will certainly not be the first time he has heard the comparison with Sideshow Bob and he has said that his response was merely good-natured and an acknowledgement of the remark directed at him, rather than part of a more devious act.

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Certainly, footage of the incident appears to show Luiz looking into the crowd and grinning before he turns around and looks back towards the melee of players who have gathered around referee Howard Webb after the incident. When the Chelsea man's response was broadcast on Sunday it provoked anger that he was taking pleasure in the dismissal of a fellow player.

The Everton captain and former United player Phil Neville tweeted "David Luiz, that's not clever". Ferguson said later: "He [Rafael] retaliates but [Luiz] quite clearly elbows him twice then rolls about like a dying swan and that convinces the referee. He was smiling. It's bad. What kind of professional is that?" Ferguson acknowledged that the challenge by Rafael was "rash".

Rafael Benitez, the Chelsea manager, said that he had not watched the incident before coming into the press conference and that he could point to "200 incidents" in the Premier League this season which had debatable outcomes. The big question facing Benitez is whether he breaks up Sunday's successful central defensive partnership of Luiz and Branislav Ivanovic for tomorrow's crucial league game against Tottenham Hotspur.

The club captain John Terry has now been an unused substitute in the last two games against Basle, in the Europa League semi-final second leg, and at Old Trafford. He is fit and wants to play tomorrow. There is a chance that Luiz could be moved into midfield, possibly at the expense of Frank Lampard.

If Chelsea beat Spurs then they will have as good as secured a place in the top four, and thus the Champions League, next season whatever happens in their final two games. Juan Mata, whose shot was deflected in for the winner against United on Sunday, said that the club could yet have a "great season".

He said: "If we are able to win the Europa League, and if we finish third in the Premier League, it will be a great season for us: winning a trophy and playing in the Champions League next season.

"Last season was tough, but at the end it was one of the greatest for the history of the club. We won two trophies. Unluckily we are not in the FA Cup final. But we are in another final in the Europa League. So if we can win this trophy and we can be third, which is better than last season in the Premier League, we have had a great season."

Mata said that a season in which Chelsea qualified for the Champions League and won the Europa League would reflect well on Benitez. Mata said: "For him and for us it will be nice, it would be great to win a trophy and to play Champions League again next season. After that I don't really know. We don't know because we are just focused on Rafa, and on winning."

Asked whether it would prove Benitez was a great manager, Mata said: "Of course he is. He won a lot of things in so many clubs, and now he has a chance to win in every game. So let's see at the end of the season."

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