Chelsea were facing an anxious wait on Monday to discover the seriousness of an ankle injury that forced captain John Terry to limp out of Arsenal's Emirates Stadium on crutches on Sunday.
The England captain had his right foot in a protective plastic cast, after Chelsea's 16-match unbeaten run ended in a 1-0 defeat that left Arsenal a point clear at the top of the Premier League.
Terry has only recently recovered from a knee injury that kept him out for seven games and also forced him to miss the end of England's unsuccessful Euro 2008 qualifying campaign.
Chelsea were also waiting to hear whether former Arsenal defender Ashley Cole would face a charge from the Football Association after Monday's newspapers printed photographs of him giving the V-sign to the home fans.
They had booed and jeered him loudly every time he touched the ball throughout the game which ended with him involved in an unseemly tangle with his former team mate Cesc Fabregas.
Arsenal could be without Ivory Coast midfielder Emmanuel Eboue for a spell after he was carried off the pitch with suspected knee ligament damage after a challenge from Joe Cole. It earned the England midfielder one of the 10 yellow cards handed out by referee Alan Wiley.
Terry had been caught by a late challenge from Eboue towards the end of the first half and losing him for the busy holiday period of matches would be a big blow to Chelsea's title aspirations. They are already without leading scorer Didier Drogba following knee surgery.
Drogba is set to link up with the Ivory Coast for next month's African Nations Cup after his rehabilitation, but whether Eboue joins him remains to be seen.
Apart from losing their most effective player in the first half, Arsenal enjoyed the better of a blood-and-guts encounter against Chelsea.
The only goal came from former Chelsea defender and the current Arsenal captain William Gallas in stoppage time at the end of the first half when the Frenchman had a free header following a corner.
Chelsea keeper Petr Cech made a rare mistake misjudging the flight of the inswinging cross from Fabregas and Gallas powered in for the only goal.
Arsenal lead the standings after 17 matches with 40 points, followed by Manchester United (39), Chelsea (34), Manchester City (33) and Liverpool (30), although the Anfield side have a game in hand.
Both Arsenal and Chelsea are in action again this week with Chelsea continuing the defence of the League Cup with a home quarter-final against Liverpool on Wednesday which could see the return of Germany captain Michael Ballack after an eight month injury layoff.
Arsenal travel to Blackburn Rovers for a quarter-final on Tuesday before facing Tottenham Hotspur on Saturday.