DAYTONA BEACH, Fla. (AP) — Welcome back, Brian Vickers.

Vickers crashed hard in his first race as Tony Stewart's temporary replacement Saturday night at Daytona International Speedway.

Vickers got loose on lap 23 of the exhibition Sprint Unlimited, triggering a six-car wreck that included Dale Earnhardt Jr., Kevin Harvick and Clint Bowyer. Vickers clipped Earnhardt's rear bumper, slid back across the track and slammed Harvick into the outside wall. The melee also involved Kurt Busch, Greg Biffle and AJ Allmendinger.

Vickers was evaluated and released from the infield care center. He finished 24th in the 25-car field. Denny Hamlin won, giving Joe Gibbs Racing its fourth Unlimited victory in the last five years.

The 32-year-old Vickers blamed a flat tire for causing him to lose control and get sideways going into a turn.

"I don't know how I cut it yet," he said. "I felt it going down the straightaway, and at that point, I started to roll out. But at that point, you're going 200 mph and there's nothing you can do."

Vickers was officially announced as Stewart's fill-in for the Daytona 500 on Friday, stepping into Stewart-Haas Racing's No. 14 Chevrolet while the three-time NASCAR champion recovers from a fractured vertebra.

Vickers was medically cleared to race earlier this week despite a recurring battle with blot clots. He raced just twice last season.

"Everyone at Stewart-Haas Racing has just put in so much into this effort, and it's such an honor to get in this car," Vickers said. "I hate that I'm in this car because it means Tony Stewart, a dear friend and someone I have so much respect for, is sitting at home. It's an honor to fill the seat, but the big focus is the Daytona 500."

NASCAR's first event of Speedweeks was supposed to get Vickers re-acclimated to restrictor-plate racing and comfortable behind the wheel. Instead, it was a short night that ended with an ambulance ride.

He can't compete while being treated for the clots because the blood thinners increase his risk of serious internal bleeding if he is hurt in a crash. He worked with doctors for a year to find the right plan that allows him to race safely and keep him protected from clots.

Vickers has three wins in 318 career Sprint Cup starts, but only raced a full schedule twice since 2009. Vickers is paired with rookie crew chief Michael Bugarewicz for the Sprint Unlimited and the Daytona 500.

Vickers was picked in part because of his success at high-banked ovals. His first career Cup victory came in 2006 at Talladega Superspeedway. He finished second in 2014 in the July race at Daytona and has made nine career starts in the Daytona 500.

Stewart, 0 for 17 in the Daytona 500, was hurt riding an all-terrain vehicle in the desert in California last week.