LONG POND, Pa. — Tony Stewart lost his pole position and will start from the back of the pack for the Pocono 500 after wrecking his car during practice at Pocono Raceway today.

NASCAR's Sprint Cup points leader lost control of his No. 14 Chevrolet and spun off the tunnel turn at the end of Saturday's first practice. The car spun into the grass, sending mud and sod flying and ripped off the nose of his car.

His Stewart-Haas Racing crew quickly got to work on the backup. Stewart became the pole sitter for Sunday's Pocono 500 when rain washed out Friday's qualifying and start positions were based on the points.

Stewart was confident he could still make a strong run in the backup.

"I feel like it's better than the primary car," Stewart said.

He posted the third-fastest practice time with a lap of 166.701 mph during the first practice Saturday and hit 164.817 with the backup in the second practice session.

"I was happier with that car then I was the first one," Stewart said. "If I'd known the second one was going to be so good, I would have crashed the first one the first lap out."

Stewart's second-place finish at Dover last Sunday shot him to the top of the Sprint Cup standings, 46 points ahead of Jeff Gordon. Stewart is the first driver/owner to lead the points since Alan Kulwicki won the 1992 Cup championship, a span of 556 races.

Stewart is trying to become the first owner/driver to win a race since Ricky Rudd at Martinsville in 1998.

He left Pocono to compete in Saturday's Dirt Late Model Dream race at Eldora Speedway, the track he owns in Ohio, and would return later that night.

The backup car was used in five Cup races in 2007 and 2008 when the team was known as Haas CNC Racing. Stewart used the chassis once this season in Las Vegas when he finished 26th.