The Associated Press

AVONDALE, Ariz. - Rookie Kyle Busch outdrove NASCAR's top contenders to win Sunday.

All but one, that is.

‘‘I just want to say I'm behind my brother 100 percent,'' the 20-year-old winner said of Kurt Busch, who was suspended earlier in the day for a Friday night run-in with police.

Standing on top of his No. 5 Chevrolet and waving to the cheering crowd at Phoenix International Raceway, Busch called his older brother, who won last year's Nextel Cup, ‘‘a true champion.''

Kurt Busch was suspended by Roush Racing earlier in the day for the last two races of the season after police accused him of reckless driving. Officers said he smelled of alcohol and was belligerent during a traffic stop near the speedway.

Kenny Wallace drove the Roush car and finished 16th.

Title contender Greg Biffle dominated the race, leading 189 of the 312 laps in the Checker Auto Parts 500. But the younger Busch, who drives for Hendrick Motorsports, used a pit stop strategy to get track position, taking the lead for the first time lap 230 by staying on track when the leaders pitted.

Biffle, who pitted, had slipped all the way to 13th for the restart. The Roush driver sliced through traffic and eventually caught and passed Busch on lap 281. But the youngster wouldn't give up, challenging the veteran and regaining the lead for good on lap 286 with a strong inside move on the mile oval.

It was the second win of Busch's career. He also won at California Speedway in September.

‘‘He had an awesome race car out there,'' Busch said of Biffle. ‘‘I want to thank him for racing me clean the whole time. That was great. I had a blast racing with him. That was fun.''

The suspension and the strong finish by the younger Busch took some of the spotlight away from the battle for the title, with leader Tony Stewart finishing behind four-time champion Jeff Gordon in fourth.

Stewart's showing, combined with a sixth-place finish by Carl Edwards, who came into the race with two straight victories, and a seventh-place run by Jimmie Johnson left Stewart with a 52-point lead over Johnson and 87 over Edwards with only next Sunday's Ford 400 at Homestead-Miami Speedway remaining.

‘‘It's a big weekend for us next weekend,'' Stewart said. ‘‘I'm glad I've got a lot of stuff to do this week, shooting a commercial Tuesday in Charlotte and the I think the whole team is going to go fishing.''