Juan Pablo Montoya spun out team mate Scott Pruett late in the race before going on to claim his first Nascar victory at the Telcel-Motorola 200 on Sunday.
The 31-year-old Montoya survived a late charge by Denny Hamlin to claim the Busch Series event, his first win in 10 races since switching from Formula One last year.
Colombian Montoya bumped front-running Pruett with eight laps to go at Mexico City's Autodromo Hermanos Rodriguez, a 2.518-mile road course.
Pole-sitter Pruett spun out and had trouble refiring his engine. He finished fifth out of 43 drivers in the 80-lap race.
"Of all the people to take out, your team mate," Pruett told ESPN television. "That was just no good, low, nasty, dirty driving. I can't put it into words. It's just so disappointing.
"If he's faster than me, we'll work it out. He can go. But not take each other out. That's just bad driving."
Montoya said he felt "really bad" about taking out his Chip Ganassi Racing team mate.
"We were both breaking about the same point," said Montoya, who piloted a Dodge Charger to victory. "He was slowing down the car a lot more. And he kind of stayed wide, so I went for the inside. And when I was there, he just turned.
"I had nowhere to go. I feel really sorry about it."
Busch races are a second-tier series on the Nascar circuit.
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