Jeff Gordon was in position for his 88th career Sprint Cup victory and sixth at Bristol Motor Speedway.
Matt Kenseth looked ready to make it two consecutive wins.
One minute they were running first and second in Sundays Food City 500 and the next they were both in the garage.
Gordon dived to the bottom groove while in the lead on Lap 391, and just as he did, he blew his right-front tire and shot back up the track and into Kenseth, who was running at full speed.
Both cars suffered extensive damage and were forced to the garage, leaving the outcome of Sundays race victory in someone elses hands.
We were setting sail, said Gordon, who ended up with a 34th-place finish. The right-front (tires) never blow up when you are up against the wall.
I dove down to the bottom to pass the No. 32 car; as soon as I got into the banking I felt the right front (tire) go. I really hate that we collected Matt in that. He had a great car.
Goodyear Tire officials said Gordons tire had a melted bead from excessive brake heat. Gordon was one of five teams that experienced the problem during Sundays race.
It was a great, great effort up until then for (us), proud of that, Gordon said. We needed points. This is definitely not going to get us any.
After four races, Gordon is 21st in points, 76 behind leader Brad Keselowski.
For his part, Kenseth said there wasnt much either Gordon or he could do to change Sundays circumstances.
I thought we had the fastest car that run, one of the only cars that could pass out there, said Kenseth, who won last weeks race at Las Vegas. And man, we just got a little behind and I just finally had it made up and wanted to be in the lead for that last pit stop.
I just had nowhere to go. We had a great car again. We just didnt make to the end unfortunately.
Kenseths 35th place finish dropped him to 13th in points, 63 behind Keselowski entering next weekends race in California.