Kenseth took advantage when Busch's dominant car got a flat with two laps to go Friday night, lifting him to his first Nationwide Series win this year and capping a record-setting day at Darlington Raceway.
"That's a lot that went down those last five laps," Kenseth said with a grin.
Nothing was bigger than Busch's tire going down.
He led 143 laps and looked like he would ease to victory. Then a late collision between Scott Lagasse Jr. and Joe Nemechek brought out the race's 10th caution and set up a two-lap sprint to the finish.
As Busch ran through the wreckage, he got a flat in his right rear tire. Busch tested the tire for several laps before rolling into the pits to loud cheers from Darlington fans.
Kenseth, who earlier set a track record to win the Southern 500 pole, still faced a green-white-checkered finish. That, too, went Kenseth's way when Morgan Shepherd spun out on the restart, ending the race.
"It's been a good day for us," Kenseth said. "Let's hope it continues."
Busch wound up 16th, a disheartening finish to what figured to be his third straight NASCAR win after last week's sweep at Richmond.
Busch did not speak to the media after the race, jumping on a golf cart and pulling away. His crew chief, Jason Ratcliff, said the team was disappointed by the dramatic turn. "But hey, that's part of this sport," Ratcliff said.
Not when Busch is rolling.
The 24-year-old has been an upstoppable NASCAR force the past two seasons. Last week, he reached 50 victories in the sport's three touring series and was ready to check off No. 51 at Darlington, where he's the defending Sprint Cup winner.
Car owner Jack Roush thought Busch's lucky streak had held up again, mishearing Kenseth on the radio and thinking it was the Roush machine's tire that had gone flat. "My heart was in my stomach," Roush said. "Man, I thought it was all over."
It was for Busch. As the cocky superstar shook his car from side-to-side behind the pace car, Kenseth thought Busch might try and stay out and pray a quick wreck would preserve victory.
Busch had no choice, though, but to slowly roll into the pits.
"It was so flat, I think I would've passed him before turn one," Kenseth said.
Turns out Kenseth barely made it that far before Shepherd, starting his 250th Nationwide event in 27 years, hit the inside wall to instantly end the race.
Brad Keselowski, racing for the first time since his surprise Sprint Cup win at Talladega, had his struggles with the "Lady In Black." Keselowski was hit from behind in turn one, lap one, then spun out twice more during the race. He finished 11th, ending a streak of five top 10s in the Nationwide Series.