 In Turn 8 Unser slowed sooner than Tracy expected (he likely couldn't see Jimmy Vasser immediately in front of Unser) and touched the championship leader's right rear tire, sending him into a tire barrier.Unser kept the car running after hitting the tires, but his chance of his fourth straight win was over.Soon after in Turn 3, Nigel Mansell spun off behind Emerson Fittipaldi, who like Unser was contemplating his moves in traffic.