Duke star freshman Zion Williamsoninjured his knee when his sneaker blew out just after the start of Number 8 North Carolina's 88-72 win over top-ranked Duke last night (February 20th). Celebrities including former President Barack Obama, director Spike Leeand Hall of Fame baseball player Ken Griffey Jr.were on hand for the game to see Williamson, the top college basketball player in the nation, but then he sprained his right knee during Duke's opening possession. Williamson slipped and fell, grabbing his knee, when the sole of his left Nike sneaker ripped loose from the shoe as he planted his foot while dribbling. Nike wished Williamson a speedy recovery and said it was, quote, "working to identify the issue." It's not know how long Williamson will be out with what was described as a mild sprain.