Philadelphia 76ers star Joel Embiid's knee injury is believed to be more serious than originally thought. Embiid is considered to have a right knee LCL sprain that is greater than a Grade 1 sprain. Philadelphia coach Doc Rivers said on Saturday that Embiid is doubtful to play in Game 1 against the Boston Celtics on Monday.

A Grade 1 LCL sprain has a possible recovery time of a few days to two weeks. A Grade 2 LCL sprain can take two to four weeks. A Grade 3 LCL sprain is in the range of four to six weeks. LCL sprains can be subject to reinjury of greater severity than the original injury.

It's unknown if Embiid is dealing with a Grade 2 or Grade 3 LCL sprain. By Monday, he'll have sat for 11 days, after missing the Sixers Game 4 victory in their first-round sweep of the Brooklyn Nets.