Arsenal manager Unai Emery has suggested that Rob Holding has sustained a long-term knee injury in the Premier League fixture at Manchester United.
The Gunners were twice pegged back by United as the two clubs played out a 2-2 draw on Wednesday night, and Arsenal's efforts were hindered by a first-half injury to Holding.
The defender needed to be stretchered down the tunnel at Old Trafford, and Emery has revealed that he expects the Englishman to be sidelined for a lengthy period.
At a press conference, Emery told reporters: "This is the worst news for us today. Rob Holding - we are going to wait for the doctors, but it is a big injury. It's his knee."
Aaron Ramsey also needed to be substituted at half time, but Emery has played down the extent of the injury picked up by the Wales international.