Chelsea will be without Damien Duff for the Christmas and New Year period after the influential winger dislocated his shoulder in the 1-0 west London derby success against Fulham at Loftus Road.
The Republic of Ireland international, whose fleet-footed runs on the flank have been central to the Blues' title challenge, fell awkwardly when challenged by Sean Davis as he fired off a shot at goal in the 22nd minute.
Duff was taken to hospital for treatment and faces three weeks on the sidelines.
Chelsea manager Claudio Ranieri said: "Damien's dislocated his shoulder and gone to hospital. It's a big blow but I hope he'll only be out for two or three weeks.
"Damien is Damien. When I don't put him in the squad my mother, who's 84, asks 'why isn't Damien playing?' She kills me about it and that's true."
Chelsea, who triumphed through Hernan Crespo's 61st-minute bullet header, are now joint top of the Premiership with Arsenal, level on points, goal difference and goals scored.