David Luíz has apparently told friends he smiled after Rafael da Silva fouled him because a Manchester United fan called him "Sideshow Bob".

The Chelsea defender was widely criticised for smiling as he lay on the turf after Rafael lashed out at his compatriot, following two elbows from the Brazilian during Chelsea's 1-0 Barclays Premier League win.

However, according to a series of reports, Luíz revealed the reason behind his grin was because a United fan had referred to him by his Simpsons moniker.

Luíz, with his mop of curly hair, bares a resemblance to Sideshow Bob, one of the show's cult characters whose criminal schemes are invariably foiled by Bart Simpson.

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Rafael and Luíz exchange words as the Brazilian departs the pitch

Manchester United manager Sir Alex Ferguson said Luíz reacted “like a dying swan” and was angered by him grinning. “That is bad,” Ferguson stressed. “What kind of professional is that?”

Assistant referee Sian Massey did not acknowledge Luíz's physical jabs but did flag for Rafael's foul before referee Howard Webb flourished the red card.

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Sideshow Bob is a cult character on The Simpsons

Luíz has previous with United from his first appearance against them in March 2011, when Ferguson was left incensed after referee Martin Atkinson failed to send him off following two off-the-ball fouls on Javier Hernández and Wayne Rooney.

The Brazilian had already scored his first Chelsea goal to equalise prior to the challenged, and the Blues went on to win the game 2-1.

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Luíz elbows Hernández in Chelsea's 2-1 win against United in March 2011

Hernández, often a thorn in the side of the centre-back, got his revenge two months later when he capitalised on Luíz's error inside the opening 60 seconds to open the scoring in United's 2-1 league victory.