NEW YORK — Nike says it’s investigating why Duke freshman Zion Williamson split a shoe open during a game against rival North Carolina. But the sportswear giant says it’s an “isolated occurrence.”

The Beaverton, Oregon-based company says it’s concerned and says quality and performance of its products are of “utmost importance.”

The shoe malfunction, which forced Williamson to leave the game with a knee sprain, happened in front of a crowd of celebrities, including former President Barack Obama and Spike Lee.

Williamson’s left shoe fell apart as he planted hard near the free throw line. The blue rubber sole ripped loose from the white shoe from the heel to the toes along the outside edge, with Williamson’s foot coming all the way through the large gap.

Nike quickly became the target of ridicule on social media, which presents challenges for the sportswear brand.

Nike’s shares are down 1 percent, or 84 cents, to $84 in early morning trading Thursday.