Manchester United have announced that James Wilson will undergo surgery on a knee injury.
The striker, who spent last season at Brighton & Hove Albion on a temporary deal, joined the Rams in the summer transfer window, but his spell was cut short when he damaged his anterior cruciate ligament in a training session.
Now it has been confirmed that Wilson will go under the knife before embarking on a rehabilitation programme.
"It's a great disappointment for him and for the club as well," said United Reserves coach Warren Joyce told the club's official website. "He's got to look to work his socks off and come back in the best shape he's ever been in his life.
"All you can do when you have setbacks is to try to be positive and look to make sure when you do return, it's in the best shape."
Derby manager Steve McClaren told the Championship club's website: "It's incredibly disappointing news that James has suffered an injury like this.
"Only last week, I was saying how much I was looking forward to working with him because he is an exciting young talent. I know that he will bounce back from this disappointment, especially as well as being a very good player, he is also a strong and determined character."
Wilson made four appearances for Derby during his short spell.