A gear failed on Danica Patrick’s Stewart-Haas Racing Chevrolet during NASCAR Sprint Cup practice at Dover International Speedway today, sending driver Jamie McMurray and Patrick’s team owner Tony Stewart into an unprotected hard wall. That’s worrying for Stewart, who is still recovering from a back injury.

Stewart missed the beginning of the season after in an ATV crash this January. Doctors are still advising him to be careful. Earlier this month, he opted to —a venue known for huge crashes—but hand the car over to Ty Dillon during the first caution.

When Danica’s car dumped oil all over Turn 4 and burst into flame, Stewart and McMurray got caught in the slippery trail it left behind. All three drivers hit a wall that was unprotected by a SAFER barrier. Stewart—perhaps the most worrisome of the three—hit the hard wall thrice.

Patrick was unhappy about Dover’s decision not to protect every possible surface drivers could hit, telling :

The ones (crashes) where you hit the wall I think I saw it’s about twice the G-load impact when you hit a non-SAFER barrier. It shouldn’t even be a question whether or not tracks have SAFER barrier all the way around. It should be mandatory. It shouldn’t be a financial decision.

Dover recently added 479 feet of SAFER barriers this year on the inside wall at the entrance of Turn 3 and the inside backstretch, reports Fox Sports. However, the outer wall on the front stretch was not protected where these three drivers hit today.

After the crash, Stewart radioed to his team, “That hurt,” but was ultimately released from the infield care center. McMurray was icing his left elbow in pain, per Fox Sports. However, all three drivers were able to rejoin the practice session when it resumed.

Stewart-Haas Racing switched to a new gear manufacturer for Dover, per . Between Patrick’s failure and an issue with the gears on Kurt Busch’s car, the team used the downtime while this crash was cleaned up to swap out the gears on all of the team’s cars.