Arsenal full-back Bacary Sagna will be out for up to three months after breaking his right leg in Sunday's defeat by Tottenham Hotspur.
Sagna fell awkwardly after an aerial challenge with Benoit Assou-Ekotto in the 2-1 loss at White Hart Lane.
The defender had a successful operation to stabilise the injury on Monday.
The Gunners have injuries to centre-backs Thomas Vermaelen, Laurent Koscielny and Johan Djourou, as well as long-term absentee Jack Wilshere.
Speaking after the game - which the home side won thanks to Kyle Walker's goal - Arsenal manager Arsene Wenger said: "We are very worried about his injury. He's in hospital.
"It is early to say but the first signs don't look good. It is the fibula and ankle and he has gone to be checked."
Sagna, 28, has been ruled out of France's final two Euro 2012 qualifiers against Albania and Bosnia, with Lille's Mathiru Debuchy called up in his place.
Wenger, meanwhile, admitted Arsenal's current realistic aim is to get back in touch with the top four rather than look at the title after their fourth Premier League defeat of the season.
He said: "At the moment we have to set ourselves a realistic target to get in touch with those teams who are fighting to stay in the Champions League. To say we will win the league is not realistic.
"We are 12 points behind Manchester United and Manchester City so it is not realistic today to say that we will win the league. We have to fight to come back into a much better position."