The Blue Devils fell hard to North Carolina after Zion Williamson went down on the opening possession. 

After taking a spill in the opening seconds and missing the rest of the game, head coach Mike Krzyzewski said postgame Wednesday night that freshman phenom Zion Williamson has a "mild knee sprain" and that his knee is "stable." Thursday afternoon, the team gave an update on Williamson's injury, describing it as a Grade 1 right knee sprain and adding that the freshman is "progressing as expected" with his status listed as "day-to-day."

Williamson was forced to the locker room after slipping while dribbling and appearing to break his shoe in the opening seconds of No. 1 Duke's 88-72 loss against No. 8 North Carolina at Cameron Indoor Stadium Wednesday night. 

Williamson grimaced and held his knee before removing his shoe and leaving the court, never to return to the game. 

Former President Barack Obama, who was in attendance at Cameron Indoor Stadium for the matchup, tweeted well wishes for Williamson's recovery after the game. 

"Zion Williamson seems like an outstanding young man as well as an outstanding basketball player," the former president tweeted. "Wishing him a speedy recovery," 

Stay tuned for more updates. This story was updated at 6 p.m. Thursday with the Blue Devils' official injury update.