USC announced that Lee was not practicing because of an "undisclosed" injury and that Coach Lane Kiffin would have an update after Saturday night's practice.
Lee, the Biletnikoff Award winner as college football's top receiver, was escorted from the field by athletic trainers on Friday after catching a pass and appearing to land on his right shoulder.
Lee set a USC record last season by catching 118 passes, 14 for touchdowns.
With Lee absent, freshman Darreus Rogers got more first-team reps and Victor Blackwell also worked at times with the first group on Saturday.
USC opens its season Aug. 29 at Hawaii.