Harris, the team's second-leading receiver last season, was injured during a 7-on-7 drill. He had been limited in what drills he was able to do this season because of having off-season knee surgery.
"He knows it and right now we are just going to take our time with him," Strong said. "We want to make sure that he's OK.
"When you make progress and then you go down, mentally it's just a toll because you put so much into it."
The redshirt sophomore caught 37 passes for 455 yards and two touchdowns last season. He missed the Belk Bowl at the end of the season after suffering a torn ACL in his right knee during bowl-game practice.
Harris also missed the 2010 season with a torn MCL in the left knee. He has also suffered a torn PCL in his right knee.
"We were just doing 7-on-7 drills," wide receiver coach Ron Dugans said. "He stuck his toe in the ground getting in and out of a break and it happened there.
"I try to be there for him and tell him that it could have been worse. There have people who have (died) on the football field. His situation could have been worse. I think he has a calling that is bigger than football. One day the whistle is going to stop blowing for him. It could be now, it could be later on but he has to understand that he's special. He has a special place in the heart of this football team."
Strong said there was no timetable for surgery.
"You just don't want to see anything like that happen to a player," Strong said.
Strong also said backup linebacker Tyon Dixon injured his foot and had surgery. He said he was unsure if Dixon would be a season-ending injury.