Arsenal look set to be without William Gallas for a 'few weeks' after the veteran defender injured his thigh in training this morning.

The Gunners face Hamburg in a crucial Champions League clash at the Emirates Stadium tomorrow, when either Philippe Senderos or Johan Djourou are likely to fill in at centre-back.

Manager Arsene Wenger said: 'We lost Gallas in the final shot of the training session. He has bruised his thigh and will be out for a few weeks.

'It is a blow because he stabilises our defence - but it is also a good opportunity for a young player to come in.