Rookie Kyle Busch out-drove NASCAR's top contenders to win yesterday.

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.

After standing on top of his No. 5 Chevrolet and waving to the cheering crowd at Phoenix International Raceway in Avondale, Ariz., 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; he has denied that alcohol was involved.

The younger Busch defended his brother, saying, "Usually, things in the media are false and that's just what it comes down to sometimes."

When he was questioned about what he meant by that statement, Busch said, "I'm not going there, bud." He then walked out of the winner's press conference.

Team representative Amy Walsh later apologized for the abrupt departure and promised Busch would return for more questions.

Unlike his younger brother, Kurt Busch made the 10-man Chase for the Nextel Cup but was running in eighth, virtually eliminated from a shot at winning another title. Kenny Wallace filled in for Busch 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 on 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 280. But the youngster wouldn't give up, challenging the veteran and regaining the lead for good on Lap 285 with a strong inside move on the mile oval.

Biffle, who needed a strong showing to hang onto at least a chance to win, was not disappointed with his runner-up finish that left him in fourth place, 102 points behind series leader Tony Stewart with only Sunday's Ford 400 at Homestead-Miami Speedway remaining.

"That is what we needed to do -- it's championship form right here," he said. "We wanted to win, but we came here and led a lot of laps and ran real strong and finished second. It just goes to show how solid this race team is."

He praised the Busch brothers, saying, "Both of those guys have a wonderful amount of talent and driving ability.

Busch went down a lap around the midpoint after pitting with a vibration, but got it back on a caution several laps later.

"It's neat for Kyle to win," Biffle said. Then, asked about Kurt's suspension, he added: "I think you'd have sympathy for anybody if you put yourself in that situation and got taken out of the racecar. But I have absolutely no information about what was going on."

It was the second win of Busch's 41-race Cup career. He also won at California Speedway in September.

"He had an awesome racecar 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 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.

"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."

Edwards, a 26-year-old in his first full season in Cup, said he was satisfied with his performance, but disappointed not to gain more on Stewart.

"We have to go to Homestead with an aggressive mind-set," he said. "We can't go there and be conservative."

Kyle Busch, in the No. 5 car, gives a thumbs-up after outlasting Greg Biffle in NASCAR's Checker Auto Parts 500.