Frank Martin told the media last Thursday that freshman Shamiek Sheppard had "tweaked" his knee in summer workouts.
Now, the third-year USC head coach fears Sheppard's injury could be more serious.
The 6-foot-6, 215-pound small forward from Brooklyn, New York, will have an MRI done Tuesday, but early evaluations don't look promising.
"Our initial response is that it's a possible ACL," Martin said. "So, we'll find out tomorrow and at least confirm it one way or the other."
Sheppard, a three-star prospect, could miss the entire upcoming season, depending on the results of the MRI.
Sheppard averaged 17 points, 11 rebounds and two assists per game in one season at Fishburne Military School in Waynesboro City, Va., before signing on to play at South Carolina.
He was one of four incoming freshmen in South Carolina's 2014 class, along with TeMarcus Blanton, Marcus Stroman and James Thompson.
Blanton and Stroman are working out with the team this summer, while Thompson's future with the program remains in doubt.
The 6-foot-9, 215-pound forward from Baton Rouge was arrested in Louisiana earlier in June on charges of aggravated battery and domestic abuse by battery.
Martin would not comment last Thursday when asked about Thompson's future with USC.
-- Martin, echoing his sentiments from last week, remained impressed with his team's progress this summer. Players who were freshmen last season are now stepping into leadership roles, Martin said.
"We have a sense of leadership in that locker room that we haven't had before," Martin said. "We have a sense of urgency, a sense of belief, because of the way we finished the year, that we're getting there.
"Guys are really starting to buy into what we can do and buy into the fact that we can win. It's exciting to be apart of it."
-- Martin said he's tired of the SEC's lack of respect as a basketball conference.
"I'm tired of this fallacy and myth that our league's no good. I think it's disrespectful to the coaches in this league," Martin said, adding later: "Trying to say that their success right now is not very good because our league is not very good - I think that's a little disrespectful and untrue.
"Our league is extremely hard. I've said it for a couple of years. We're in transition, and I think our league is now starting to take shape. Coaches are establishing their programs."