Arsne Wenger has revealed he had to rush Ashley Cole back early because Pascal Cygan has a hamstring problem.
Cygan has been playing at left-back in place of Cole since October, and today made way for the England international as he limped off in the first half against Middlesbrough.
Wenger says the problem could keep Cygan out for as much as three weeks.
"He looks to be out for three weeks. It looks to be a hamstring but they are not exactly sure. If it's a real hamstring then it's 21 days."