Bournemouth's England midfielder Lewis Cook will be sidelined for six to nine months with a ruptured anterior cruciate ligament (ACL), the club announced on Thursday.
The 21-year-old suffered the serious knee injury during the 2-1 Premier League victory over Huddersfield on Tuesday.
Cook was assessed by the club's medical staff after the game and further assessment and scans on Wednesday revealed the extent of the damage to his right knee.
"We are all devastated for Lewis," Bournemouth manager Eddie Howe told the club's official website.
"It is a huge blow to a very talented player who has been a very important part of our side over the last 18 months.
"But Lewis is a strong character who only has to look around our dressing room for inspiration of how an injury like this is merely a setback and to know that he can come back better than ever."
A defiant Lewis tweeted: "Thank you for all your kind words, I am devastated with my injury but this is just a bump in the road. I’ll be back stronger and better. The hard work starts now."