Kyle Busch became the youngest winner in NASCAR's top series last night, a feat that was almost an afterthought with most of the focus on the battle for the final spots in the Chase for the Championship.

At the end of Sony HD 500 in Fontana, Calif., the bottom half of the top 10 in the Nextel Cup point standings was shaken up, with Matt Kenseth and Jamie McMurray in and Ryan Newman and Jeff Gordon out with only one more race before the start of the 10-man, 10-race finale.

That didn't bother the 20-year-old Busch, the brother of reigning Cup champion Kurt Busch, as he celebrated his breakthrough victory at California Speedway.

"It's unbelievable," said the rookie, whose previous best finishes were seconds this year in Las Vegas and Dover. "We should have been here at least five times this year, but we haven't been able to close the deal."

The previous youngest winner was Donald Thomas, who was four days older than Busch when he won in Atlanta in November 1951.

Driving a Chevrolet for Hendrick Motorsports, Busch led 95 laps on the way to the victory in his 31st career start.

Busch was leading on Lap 240 when debris brought out the 10th of 11 cautions in the race. With the race scheduled to end on Lap 250, Busch faked as if he was going to pit on Lap 241 and, when all the other leaders followed, he went ahead and pitted.

His crew put on only two tires and Busch was able to beat everyone else back onto the track and hold the lead to the end.

"My nerves were getting to me," Busch said. "When I made that last pit stop [under caution], everybody followed me in and I thought, 'Cool, we're going to be all right.' That stop is what got us the win."

While Busch took control late in the race that was extended to 254 laps because of a caution period, the battle within a battle was raging for positions in the standings.

Only the top 10 drivers in the points following Saturday night's race at Richmond will be eligible to contend for the championship in the last 10 races of the season.

Greg Biffle, already solidly in the Chase, finished second, followed by Brian Vickers, Carl Edwards, series points leader Tony Stewart and Kasey Kahne. Vickers is Busch's teammate.

Kenseth, coming off his first victory of the season last week in Bristol, had another strong race, finishing seventh. He has charged from 17th in the points following the Pocono race July 24.

"We've run much better and you know the guys that have been around us in the points have had some trouble and maybe haven't run as well in the second half of the year," he said.

* FORMULA ONE: Juan Pablo Montoya won the Italian Grand Prix from the pole, and Fernando Alonso finished second to maintain the inside track on the Formula One season championship.

Montoya recorded his sixth career victory and second at Monza, where he won his first Grand Prix in 2001. Ferrari's Michael Schumacher finished 10th, mathematically ending his run of five straight world titles.

Kyle Busch, driving his Chevrolet down the backstretch at California Speedway, led for 95 laps at the Sony HD 500.