Little more than two hours before the Warriors' season opener Tuesday night against Houston, on a TV in a back room at Oracle Arena, Steve Kerr and members of his staff watched Celtics small forward Gordon Hayward sustain a gruesome ankle injury minutes into his Boston debut. "It was just terrifying," Kerr said. "The whole coaching staff was just devastated watching it." Hayward was diagnosed with a fractured left ankle, which could sideline him the entire season. It reminded Golden State, heavy favorites to win a second straight NBA title, that nothing is guaranteed. Even a cast of All-Stars in their prime can't prevent a season-altering injury.