Arsenal have been rocked by the news that former Chelsea defender William Gallas faces several weeks on the sidelines with a thigh strain.
The Frenchman suffered the injury while training for the crucial Champions League encounter against Hamburg.
Gunners boss Arsene Wenger confirmed: "We've lost Gallas in training. He pulled his thigh and will be out for a few weeks.
"It's a blow because he stabilises our defence but it's a very good opportunity for a young player to come in and show he is good.
"We wanted him to be fit to play, not only because of his quality, but because of the number of games we have now until January."
However, it was not all gloom and doom at the Emirates Stadium as both Freddie Ljungberg and Robin van Persie came through the training session unscathed and are available for selection against the Bundesliga side on Tuesday.
Van Persie suffered an ankle injury in the 1-1 draw against Newcastle United on Saturday but an X-ray showed the knock was not serious while Ljungberg has finally recovered from a thigh in jury that had sidelined him since the end of September.