Sunderland boss Martin O'Neill is hoping that Stephane Sessegnon's injury turns out to be just cramp and nothing more serious.
The Benin international was the Black Cats hero on Wednesday night when he fired Sunderland to an extra time victory over Boro at the Riverside before limping off the field.
O'Neill is now keeping his fingers crossed that Sessegnon will be fit to face the Gunners in a double header, this weekend in the Premier League and next in the fifth round of the FA Cup.
O'Neill said: "He is an outstanding player and I am delighted that we have him.
"He's really great. He hasn't missed a game - I hadn't realised he hasn't missed a game this season for us, which is outstanding.
"I hope it is just cramp rather than anything else."