Arsenal central defender William Gallas will be out for "a few weeks" after suffering a thigh injury in training today, coach Arsene Wenger said.

Wenger, whose side were preparing for Tuesday's Group G Champions League game at home to Hamburg SV, said the Frenchman suffered the injury at the very end of the session at their London Colney base.
   
"We've lost Gallas in the final shot of training," Wenger told a news conference. "He pulled his thigh and will be out for a few weeks.
   
"It is a blow because he stabilises our defence. As well, it's a good opportunity for a young player to come and show that he's good.
   
"But of course, overall, we wanted him to be fit -- not only because of his quality but as well because of the number of games we have coming up...we are playing three times a week."
   
Losing Gallas, who joined from Chelsea on transfer deadline day in August in a swap with Ashley Cole, is a major setback for Wenger both in Europe and domestically.
   
Swiss internationals Johan Djourou and Philippe Senderos would be the main candidates to replace him on Tuesday, when last season's finalists need to get their campaign back on track.
   
Arsenal, who beat Hamburg 2-1 away in a promising start in Group G, have taken only a point from their last two games against CSKA Moscow and are level on seven points with Porto.
   
With the Russians top on eight points and Hamburg out of the running after four straight defeats, Arsenal's campaign will go down to their final match at Porto on December 6th.
   
Wenger said two players who missed Saturday's 1-1 draw at home to Newcastle United - Brazilian midfielder Gilberto, who returned home for family reasons, and Fredrik Ljungberg, who lacked match fitness after injury, were ready for duty.
   
Dutch forward Robin Van Persie, who limped out of the Newcastle game but trained on Monday, is also fit.

Looking ahead, Wenger said: "There's a still a lot of work to do...and we have to be more dynamic than against Newcastle in the first half. That was not how we want to play football.
  
"It's a must-win game for us."
   
However, he denied Arsenal would now focus on Europe rather than the Premier League, where they trail leaders Manchester United by 12 points.
   
"I really want to win both," he said. "Every time we don't win a game it hurts me so much, whether it's a championship or a Champions League game. It hurts exactly the same."
   
Asked if it would be a disaster if Arsenal failed to make the next round after reaching last season's final against Barcelona, he said: "Every time Arsenal don't win something it is a disaster for me. Every game we don't win is a real disaster."