Arsenal will be without midfielder Alex Song for their Champions League clash at Barcelona on Tuesday.
Song suffered a groin injury during the 1-0 win over Wolves on Saturday and missed training on Monday, and Arsene Wenger has now confirmed that he will not be part of the squad to head to Camp Nou.
Wenger said: "It was a bad surprise this morning. He had a scan yesterday afternoon on his knee and it is inflamed cartilage.
"We will have to wait and see how serious it is but he is completely out of the squad for tomorrow's game."
Thomas Vermaelen looks certain to take one of the central defensive berths but, with William Gallas and Song both missing, Wenger may be pressed into an uncomfortable call on veteran Sol Campbell's match fitness, with Mikael Silvestre his only other first-team option.
"That will be a decision I will have to make," Wenger said on Campbell, whose advancing years have led to careful management of his workload. "We have to be conservative with him and see how he feels after today."
Arsenal are already without Cesc Fabregas and Andrei Arshavin for the match, while Robin van Persie is still at least two weeks away from a return.
Arsenal came back from 2-0 down to secure a 2-2 draw at Emirates Stadium and will need to score at Camp Nou if they are to progress.