Arsenal fear Rob Holding has suffered a season-ending cruciate ligament injury.
The central defender suffered a serious knee injury in the 2-2 draw at Manchester United on Wednesday.
Holding has been undergoing numerous tests to determine the extent of the injury. But there is real concern that Holding could have damaged his cruciate.
Arsenal are still to confirm the extent of the injury and will hope for positive news in the next 24 hours.
Manager Unai Emery fears Holding faces a lengthy spell on the sidelines. He said on Thursday: 'The first news is not good.