Robert Covington will be sidelined one to two weeks with a sprained right MCL, according to a source.
As a result, the 76ers small forward could miss the first two to six games of the regular season.
Covington had an MRI on Saturday after suffering the injury in the fourth quarter of Friday's 81-65 setback to the Boston Celtics in Manchester , N.H.
Covington suffered the game-ending injury while driving to the basket with seven minutes remaining.
"I got hit in it," he said of his knee. "I was like driving and the defender tried to cover and hit into my knee. And I hit it on the floor as well."
The 6-foot-9, 215-pounder was carried to the locker room by teammates and needed crutches to get around after the game.
The source said Covington is feeling better and was able to put pressure on his knee Saturday.
The Chicago native will be huge loss, averaging 13.2 points, 5.5 rebounds and 2.3 assists last season.