Julio Cesar has apologised on the Queens Park Rangers website for dressing up as David Luiz at the Chelsea's defender's 26th birthday party.
The Brazilian goalkeeper is good friends with his compatriot and donned a Chelsea shirt and wig to go to the fancy dress bash.
But some Rangers fans were unhappy about it, given that the two sides are west London rivals and the R's have endured a poor season which seems destined to end in relegation.
West London rivalries: Julio Cesar (left) pictured in a Chelsea shirt at David Luiz's (centre) birthday party
Buddies: Cesar and Luiz are good friends away from the pitch and often spend time at the latter's flat
Cesar issued a statement reading: 'I would like to clarify that last night I attended David Luiz's fancy dress birthday party and, as a joke for my friend, my family and I dressed as him.
'I want to assure everyone that absolutely no offence was intended.'
Cesar's wife Susana Werner posted the picture on her Instagram account but it was subsequently deleted.
The club's head of communications Ian Taylor wrote: 'The club is aware of an image of Julio Cesar circulating on social networking feeds.
How many Chelsea players can you spot? Paulo Ferrerira as Robin (bottom left), Oscar as Zorro (centre), Eden Hazard in a Brazil shirt (right), Nathan Ake as Superman (top right), Ramires and Luiz as Chelsea Pensioners (centre)... and is that Henrique Hilario (left) as a pilot?
Don't eat too much! Luiz had two cakes including one with the word 'geezer' on
'The image, which appeared on an Instagram account, has since been deleted. The club will be dealing with this issue internally.'
Other pictures from the bash surfaced too - including Gary Cahill in a not-very-fetching baby outfit.
Youngster Nathan Ake turned up as Superman, while birthday boy Luiz and his good friend Ramires seemed to be dressed as Chelsea pensioners.
Stalwart right-back Paulo Ferreira was Robin but Batman was nowhere to be seen - and Oscar turned up as Zorro - perhaps inspired by the mask that his colleague Fernando Torres has been wearing recently.
Robin Hood? Marko Marin with Luiz, dressed in a little green outfit