Nike says it will look into what caused a basketball shoe being worn by Duke freshman forward Zion Williamson to come apart during his first game against rival North Carolina, Wednesday night.

Williamson was wearing the Nike PG 2.5 Oklahoma City Thunder star Paul George’s signature shoe in a Duke colorway exclusive. Just after the tip-off, somehow, the blue rubber sole came undone on the outside edge and ripped from the white shoe, causing Williamson’s foot to come out of the large gap.

READ MORE: NBA, FIBA set to launch league in Africa — with assist from Obama

The 6′ 8″ forward swiveled and then came down holding his right knee. He soon left the game, walking to the locker room shoeless and with a slight limp.

President Barack Obama was at the game, sitting along the baseline near the Duke bench. He shouted words of encouragement to Williamson as he left the court.

READ MORE: Barack Obama attends Duke basketball game and tweets support for injured Zion Williamson

After the game, Duke coach Mike Krzyzewski called it a “mild knee sprain,” but didn’t offer any further detail, aside from saying Williamson’s knee was stable. The star player is expected to undergo further testing, with results coming in on Thursday, according to ESPN.

In a statement, Nike said it will look into what caused the sneaker to come apart.

“We are obviously concerned and want to wish Zion a speedy recovery,” Nike said in a statement, according to ESPN. “The quality and performance of our products are of utmost importance. While this is an isolated occurrence, we are working to identify the issue.”

The incident caused some heat to Nike as well. Nike’s stock dropped, causing ESPN host, Jay Williams to tweet:

According to ESPN, Duke is four years into a 12-year contract with Nike as the exclusive supplier of its uniforms, shoes and apparel.ESPN added that Nike has worked exclusively with the university since 1992.

In Wednesday night’s game, the Tar Heels beat the Blue Devils 88-72. It marked their first win playing at Duke since 2016.

READ MORE: NBA likely to ban Kanye’s latest ‘Yeezys’ over flashy design