Arsene Wenger confirmed that William Gallas could be out of action for a number of weeks following Arsenal's 2-0 win over Porto in the UEFA Champions League.
The French international pulled up with a hamstring injury in the dying moments at Emirates Stadium, and had to be substituted with Alexandre Song taking his place.
Gallas is now expected to miss the next few weeks of the season, pending further examinations on Wednesday morning, after starting his Gunners career in impressive fashion since a deadline day move from rivals Chelsea.
Wenger confirmed he expects to lose Gallas for Saturday's trip to The Valley to play Charlton, and most likely longer with his participation in France's upcoming Euro 2008 qualifers now in doubt.
"We have bad news about Gallas," he told Sky Sports News.
"It does not look good for Saturday and maybe longer, it is hamstring, and it looks like a strain."
Arsenal also lost Johan Djourou to injury during the warm-up for the Porto game, as Justin Hoyte came in for a suprise start at left-back with Gallas shifted across to partner Kolo Toure.