Benji Kimpioka suffered a hamstring injury in Sunderland U23s' win at Aston Villa on Friday which could keep him out until the New Year.
The striker was substituted midway through the second half of the 2-0 victory at Villa.
And the injury means the 20-year-old will face up to two months out of action, which would make it unlikely he will play again in 2020.
Kimpioka has been in good form for the U23s since signing a new deal with the club at the beginning of the month, scoring four goals in as many outings in Premier League 2.
The Sweden U21 international would likely have been one of those youngsters Phil Parkinson intends to bring into the first team over the next 10 days as Sunderland prepare to take on Mansfield Town in the FA Cup first round next Saturday, and then play at Fleetwood Town in their final EFL Trophy group game a week on Tuesday, but this injury has put paid to those plans.
Kimpioka's injury was the only negative to come out of the U23s' win at Villa's Bodymoor Heath training ground.
Elliot Embleton continued his comeback from the thigh injury he suffered in pre-season, and scored both goals - putting the Black Cats in a matchwinning position within 20 minutes.
The victory lifted the U23s to sixth place in the table, with Villa immediately above them on goal difference.
