Kurt Busch won at Texas Motor Speedway on Sunday, taking over the lead with 2½ laps left when his younger brother's car suddenly slowed down on the backstretch after leading 232 laps.
Johnson, the series points leader trying to become the first Sprint Cup driver to win four consecutive season championships, wrecked on the third lap.
His crew needed more than an hour to repair and basically rebuild his No. 48 Chevrolet, but he returned to finish 38th. His points lead with two races left was cut from 184 to 73 ahead of Hendrick teammate Mark Martin, who finished fourth.
Kyle Busch won the Nationwide and Camping World Truck races at Texas, and was trying to become the first driver to win in all three of NASCAR's national series on the same weekend.