(Reuters) - Shares of Nike Inc fell nearly 2 percent on Thursday, a day after a sneaker worn by emerging basketball star Zion Williamson split in half 33 seconds into a hotly anticipated game between Duke University and North Carolina.
The freshman center, who plays for the Duke Blue Devils, suffered a mild sprain to his right knee, according to his coach Mike Krzyzewski.
Williamson did not return to play, which ended with No. 1 Duke losing 88-72 to the No. 8 ranked Tar Heels.
"We are obviously concerned and want to wish Zion a speedy recovery," Nike said in a statement.
"The quality and performance of our products are of utmost importance. While this is an isolated occurrence, we are working to identify the issue."
Williamson was wearing the Nike PG 2.5 basketball shoe when he was injured, according to ESPN.
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Nike shares were down 1.9 percent at $83.40 in early trading on the New York Stock Exchange, while its relatively thinly-traded shares on the Frankfurt market fell around 1 percent. Shares in rivals Adidas and Puma edged higher.
Nike is Duke's exclusive supplier of uniforms, shoes and apparel under a 12-year contract that was extended in 2015 and has had an exclusive deal with the private university since 1992, ESPN reported.
Williamson, who averaged 21.6 points a game, has been tipped as the "next Lebron James" and is expected to be selected first in the NBA draft this June.
Krzyzewski said it was unclear how long Williamson would be out because of the injury.
The game between the interstate rivals and two of college basketball's best teams was the marquee match so far in the season with tickets selling for thousands of dollars, according to multiple news outlets.
Former President Barack Obama, director Spike Lee and star NFL running back Todd Gurley attended the game at Cameron Indoor Stadium, the home court of the Duke Blue Devils.
(Reporting by Brendan O'Brien in Milwaukee, Siddharth Cavale in Bangalore and Sudip Kar-Gupta in Paris; Editing by Keith Weir, Bernard Orr)