Tony Stewart hadn't even gotten his car up to full speed Friday at Richmond International Raceway before it was back to the drawing board for his Joe Gibbs Racing team.

Stewart crashed in the opening moments of practice on the .75-mile oval, sending the No. 20 team scrambling to ready the two-time and defending NASCAR Nextel Cup champion's backup Chevrolet Monte Carlo.

Not an auspicious way to begin a week in which Stewart's still fighting to wrap up a spot in the Chase for the championship.

Stewart goes into Saturday night's Chevy Rock & Roll 400 eighth in the standings, only 45 points in front of 11th-place Kasey Kahne, the one driver outside the top 10 with a chance to race his way into NASCAR's 10-race post-season run. Ninth- and 10th-place Mark Martin and Jeff Burton are both within 15 points of Stewart.

Stewart said his car slid up the banking into the slickest part of the track before he lost control.

``There was just no grip,'' Stewart said. `` Being in those marbles, I couldn't keep the back end underneath me.''

Fortunately for Stewart, it was a very long practice session, giving him the opportunity the get the backup car up to speed.

``It came around right there at the end, which I'm happy about,'' Stewart said. ``If I didn't run that last run, I'd be a lot more nervous than I am right now. But that last run was really good.''

Even so, he'll have to come from the rear Saturday night after qualifying 40th.

It's the fourth time in his career that Stewart has had to go to a backup car during a race weekend. The other times were at Chicagoland Speedway in 2004 and 2005 and at the fall Bristol race in 2005. He finished first and fifth in the two Chicagoland events and eighth at Bristol.