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.