DAYTONA BEACH, Fla. — Dale Earnhardt Jr. triggered a nine-car accident in the Daytona 500 that knocked rival Kyle Busch out NASCAR's biggest event of the year.

Busch had led a race-high 88 laps before the accident, which came just after a restart with 75 laps to go in Sunday's race at Daytona International Speedway.

Earnhardt had just made his second mistake of the day in the pits under a previous caution when he pulled his Chevrolet too far out of his stall during a service stop. He was penalized one lap and returned to racing intent on putting himself in position to get back onto the lead lap.

He was racing with Brian Vickers, also a lap down, who blocked the move by pushing Earnhardt down below the yellow out-of-bounds line. When Earnhardt re-entered the racing surface, he clipped the left-rear corner of Vickers' car to trigger the accident.

"My goal is to keep Junior behind me," Vickers said. "I went to block him. I beat him to the yellow line and then he just turned us. To wreck somebody intentionally like that in front of the entire field is really kind of dangerous. That's my problem with it."

Vickers also wondered why NASCAR did not penalize Earnhardt for aggressive driving, particularly since it issued a five-lap penalty to Jason Leffler in Saturday's Nationwide Series race for a similar incident.

Busch, who was racing the approaching rain for his first Daytona 500 victory, said the accident was senseless.

"Some guys having some bad days and not doing their best out there, just made their bad day our bad day," Busch said. "It's just a shame. It's just unfortunate that two guys got together that were a lap down that were fighting over nothing."

Three-time defending series champion Jimmie Johnson, Kurt Busch, Robby Gordon, Denny Hamlin, Jamie McMurray, Scott Speed and Carl Edwards also were caught up in the accident, which sent Vickers to the garage.