Sheffield United could be forced into transfer market to replace Harry Chapman

Blades boss Chris Wilder revealed Middlesbrough's on-loan winger has been ruled out for three to four months after suffering ankle ligament damage in training.

His loan expires next month, and United had been keen to extend the deal until the end of the season.

United will now monitor his progress over the next month, before deciding on their next move.

Wilder said: "We have an option in January to extend it. We'll get all the details and work something out.

"We'd like to keep the player but obviously if he's not going to be involved until really late on in the season, we're going to make that decision.

"We would have extended it (the loan), so if he doesn't sign, we will be one player light in that position."

After exiting the FA Cup at Bolton Wanderers on Sunday, it has been a miserable start to the week for the Blades.

"I think it knocked the players back, just the manner of what happened," said Wilder. "It was a disappointing week really.

"It was an innocuous situation, no one anywhere near him.

"It's desperate news for him because he has become quite an important player for us. He was going to play on Sunday against Bolton.

"These things happen, the boy will get over it. He'll have the best medical attention from his parent club and whatever we can do as well as a football club.

"It was just the manner in how it happened really but it's not the first and it won't be the last time something happens on the training ground.

"It's an unfortunate situation and he's going to be out for quite a while.

"He's ruptured a ligament in his ankle so it's going to be three or four months.

"He's going to need an operation. It takes him well into the New Year."

Chapman has made 11 appearances for the Blades so far this season, scoring four goals, including a hat trick in the FA Cup win over Leyton Orient.