BRISTOL, Tenn. (AP) -- Danica Patrick wrecked just minutes into what turned into a dicey first practice session Friday at Bristol Motor Speedway.
In all, four drivers had to go to backup cars before the halfway mark of the 90-minute session, including 15-time Bristol winner Kyle Busch.
Denny Hamlin, who watched the first 15 minutes of practice from pit road, attributed the wrecks to drivers adapting to NASCAR's new aerodynamic rules and Goodyear's tire compound producing faster speeds.
''I really don't think it's treacherous,'' Hamlin told Fox Sports 1. ''It's just the speeds are so much higher than we've seen. It takes a little getting used to. We are all out there fighting for a tenth-of-a-second, a hundredth-of-a-second at Bristol. I think it comes more from us pushing the edge than it is treacherous.''
Patrick was the first to wreck, losing control roughly three minutes into the session. She slammed into Parker Kligerman's car, and his Swan Racing team appeared to be trying to fix his Toyota as Stewart-Haas Racing immediately pulled out the backup Chevrolet for Patrick.
Justin Allgaier then hit the wall, then Busch. Moments later, Greg Biffle crashed. All three went to backup cars.
Ricky Stenhouse Jr. later scraped the wall, but didn't appear to do much damage.
Ryan Newman, who missed the first 15 minutes of practice because of a penalty last week at Las Vegas, found the beginning of practice entertaining.
''We sat there and watched a few guys crash,'' he said. ''It seems like the cars are really, really sensitive to some changes just because the cars are so stiff now because of the rigidity of how we're running them. Once you lose it, you really lose it, which is what we've seen.''