Arsenal are sweating on results of a scan William Gallas underwent last night on injured knee.
The Arsenal defender limped off in the first half of the Champions League quarter-final with Villarreal after twisting a knee.
Boss Arsene Wenger fears Gallas, 31, could be out for a long time after damaging medial ligaments.
Manuel Almunia - who also came off against the Spaniards with a recurrence of an ankle problem - is hopeful he will be fit for next week's second leg.
The Arsenal keeper had a scan on his injured right ankle after the 1-1 draw but the problem is not thought to be very serious.