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's shares are down 1 percent, or 84 cents, to $84 in early morning trading Thursday, some $1.12 billion in value.

Despite that, Portland Business Journal reporter Matthew Kish, who covers Nike, said the financial impact would be minimal.

There will be short-term damage to the Nike brand but no long term impact, he said.

"Nike has $36 billion in annual sales," Kish said. "Basketball is only four percent of that at about $1.6 billion. So while it's important and high profile, the potential damage I would say overall to the brand is a little limited.

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In the 2015 Berlin marathon, Eliud Kipchoge of Kenya won the race but missed a world record. He began having problems with the soles of his Nike shortly after the start and finished with them slipping out out the shoes.

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