Nike Inc.’s (NKE) reputation as the world’s number one sports brand took a serious hit on Wednesday night.

Star U.S. college basketball player Zion Williamson, one of the best NBA prospects in the past decade, limped off seconds into a closely followed contest between Duke University and North Carolina after his foot broke through his Nike-made shoe. Williamson twisted his knee and fell to the floor after one of his sneakers gave out, forcing him to leave the game.

Former President Barack Obama, who was in attendance, was captured on video saying “his shoe broke!” with a look of shock on his face. Within minutes, social media users pitched in, aiming digs at Nike and its shoe brand.

According to Bloomberg, the incident was top of the worldwide trending list on Twitter. Even rival brand, Germany’s Puma SE (PMMAF), got involved, tweeting from its official account “Wouldn’t have happened in Pumas.”

Investors were understandably anxious. Nike’s stock fell 1.17% in after-hours trading, reflecting concerns that its shoes are defective and that Williamson’s resulting injury could lead the firm to miss out on signing a player believed to be the next great basketball superstar when he goes pro this summer. The company generates about 62.2% of its revenues from sneakers.

In a statement, obtained by ESPN, Nike was quick to point out that Williamson’s shoe breaking was an “isolated occurrence” and one it is looking into.

"We are obviously concerned and want to wish Zion a speedy recovery," the company said. "The quality and performance of our products are of utmost importance. While this is an isolated occurrence, we are working to identify the issue."

Wednesday nights mishap isn’t the first time that the quality of Nike’s basketball merchandise has been called into question. Multiple jerseys starting ripping after the company took over as the official NBA uniform supplier in 2017.