Arsenal will be without both Abou Diaby and Thomas Vermaelen when they face Portuguese side Braga in their opening Champions League group game on Wednesday.
Diaby injured his ankle during the Gunners' 4-1 win against Bolton Wanderers on Saturday while Belgian defender Vermaelen has an Achilles problem.
Meanwhile, boss Arsene Wenger has backed north London rivals Tottenham Hotspur to have a successful European campaign.
Spurs have been placed in a tough Champions League group after being given a scare by Young Boys in the play-offs, but Wenger believes Harry Redknapp's squad is strong enough to do well in Europe's premier competition.
He said:"It is hard for everybody but Tottenham have a quality squad. They have brought William Gallas and Rafael van der Vaart and, if you look at the number of players they have now, you don't even speak about David Bentley who they bought for £17million.
"They have Robbie Keane, Nico Krancjar, Luka Modric, Van der Vaart, Roman Pavlyuchenko, they have the quantity. In central defence I don't know but they must have six or seven central defenders so they have a big enough squad to deal with the physical demands.
"I believe you adapt to this level of football very quickly, the difficulty is to switch quickly from Champions League to the championship because the Premier League is very demanding. That is difficult, but they have a big squad. They haven't done it by accident and I believe they have what it takes."