Arsenal manager Arsene Wenger confirmed defender Laurent Koscielny will be out "for a while" after he was taken off with a deep cut during the club's 6-3 defeat by Manchester City on Saturday.
He suffered the cut on his knee when he tried to prevent Alvaro Negredo from scoring City's second goal.
"He has a cut and he'll be out for a while, but for how long I don't know," said Wenger.
Thomas Vermaelen and Per Mertesacker are Arsenal's only other centre-backs.
Wenger has also used full-back Bacary Sagna in central defence this campaign.
France international Koscielny, 28, and fellow central defender Mertesacker have been part of one of the tightest defences in the Premier League this season.