Arsenal midfielder Mathieu Flamini has been ruled out of action for three weeks.
Flamini faces a spell on the sidelines after suffering an ankle injury during Tuesday's heartbreaking UEFA Champions League defeat to Liverpool.
The French international was stretchered off before half-time at Anfield after sustaining the injury and scans have shown the full extent of the problem.
It means Flamini will miss this weekend's vital showdown with Manchester United, live on Sky Sports 1.
Gunners boss Arsene Wenger admitted it was a major blow to lose the key midfielder with Gilberto Silva likely to replace Flamini in the Arsenal engine room at Old Trafford.
"I believe Mathieu will be out for three weeks," Wenger told the club's official website.
"It is a big blow but Gilberto has a lot of quality and experience. He will come in. He can help the team recover and focus.
"Apart from that we don't have any other injuries from Tuesday. We have a few bumps and bruises but nothing special.
Wenger also confirmed Robin van Persie is fit for the trip to United after recovering from a thigh problem, but Bacary Sagna was still missing.
"Robin van Persie is available. He had two good sessions yesterday and today," added Wenger
"He looks to be OK and we'll see how we go from here. But Bacary Sagna is out."