Arsenal expect captain William Gallas to be sidelined for three weeks with the groin injury he suffered at Blackburn.
The defender went down in agony off after hurdling a 24th-minute challenge from Roque Santa Cruz in Sunday's 1-1 Premier League draw.
He immediately called for assistance from the bench and, a few minutes later, hobbled off to be replaced by Philippe Senderos.
'He has done his groin, I knew it straight away,' manager Arsene Wenger said on the club's official website.
'He will be out for three weeks.'