Borussia Dortmund midfielder Youssoufa Moukoko has been ruled out for the rest of the season after suffering an injury in training on Friday.
The 17-year-old, who joined the Bundesliga club from Manchester City last summer, had made just two appearances for Dortmund this season before he was forced off with a knock to his knee.
Moukoko is expected to undergo surgery and is likely to be out for several months.
The youngster's absence will be a major blow for Dortmund, who have struggled to find form since the arrival of coach Thomas Tuchel earlier this year.
Tuchel has brought in new signings such as Erling Haaland and Jadon Sancho, but the team's defensive record has been poor and they have struggled to score goals.
Dortmund currently sit bottom of the Bundesliga table with only one win all season.
The injury comes at a difficult time for the club, who are still trying to overcome the loss of key players such as Marco Reus and Pierre-Emerick Aubameyang.
With the Champions League group stage looming, Dortmund will need to find ways to cope without their star player.
But for now, the focus must be on getting Moukoko back to full fitness as soon as possible.
It is hoped that he can make a swift recovery and return to action in the coming weeks or months.
In the meantime, Dortmund will need to rely on their other midfielders to step up and fill the void left by Moukoko's absence.