AVONDALE, Ariz. — One took the checkered flag. The other was booted from his car before the race even began.

Those Busch brothers had some kind of Sunday.

A few hours after older brother Kurt was suspended for the final two races of the season for his run-in with police earlier in the weekend, 20-year-old Kyle won the Checker Auto Parts 500, his second Nextel Cup victory in 41 starts.

"I just want to say I'm behind my brother 100 percent," the younger Busch said after standing on top of his No. 5 Chevrolet and waving to the cheering crowd at Phoenix International Raceway.

Kurt Busch, the defending Nextel Cup series champion, won at Phoenix in the inaugural April NASCAR race this year. But team owner Jack Roush, under pressure from sponsors that include liquor manufacturer Diageo, suspended Kurt because of his allegedly belligerent behavior during a traffic stop near the raceway.

The elder Busch was cited for reckless driving. Sheriff's deputies said Busch smelled of alcohol, but no citation was issued after a breathalyzer test was inconclusive because the device malfunctioned.

Little brother Kyle more than upheld the family name, winning a late side-by-side duel with Greg Biffle then pulling away over the last 25 laps on the 1-mile oval.

Lost in the Busch banter was the race's impact on the battle for the title, which will be determined Sunday in the season's final race at Homestead-Miami Speedway.

Tony Stewart, who finished fourth, holds a 52-point lead over Jimmie Johnson, who was seventh. Carl Edwards is third, 87 points down. Edwards finished just ahead of Johnson in sixth place.

Stewart, the 2002 champion, needs only to finish ninth or better to wrap up the title, no matter what his competitors do. He goes to Homestead having finished ninth or better in 19 of the last 21 races.

"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."

When it was over, Kyle became upset with a question about his brother and walked out of the postrace news conference. Cooled down, he returned 20 minutes later to finish the session without any further confrontation.

"I had the best car for a major part of the day," said Biffle, who led for 189 of the 312 laps. "I don't know what happened."

Kyle entered the news conference, repeated the support for his brother, then added, "Usually, things in the media are false and that's just what it comes down to sometimes."

A Nextel Cup media representative asked that no further questions be asked about Kyle's brother. But the media remark irked a roomful of reporters, and one asked exactly what false things had been reported about Kurt's problems.

"I'm not going to go there, bud," Kyle said. "That's a very, very inappropriate question to ask."

Then the winner got up and stalked out. When he returned, he tried to amend his comments.

"There is a lot of speculation out in the media," he said. "And the only things that are out there to acknowledge is the police report and any information Kurt Busch chooses to release in the future."

Although just out of his teens, Kyle Busch had no problem shrugging off the distraction of his brother's situation.

"Whether or not you're on the rocks with your girlfriend or you're doing whatever else outside the racetrack, you come in here and get in that race car, you're focused and you're down to one duty, and that's obviously to win the race."

Busch used shrewd pit stop strategy to take the lead for the first time on lap 230. Biffle pitted when Busch didn't, then had to fight his way back from 13th place.

Biffle eventually passed Busch on lap 280, but Busch stayed with him. The two were side-by-side on several occasions before Busch's Chevrolet slipped to the inside past Biffle's Ford to take the lead for good on lap 285.

"You've got to remember I came from 13th," Biffle said, "and just caught him and ran him down. That just uses up so much of the tires. I just didn't have enough left when I got there."

Jeff Gordon, Busch's teammate who finished third, was surprised the youngster beat Biffle.

"I didn't think anybody had anything for the No. 16 car (Biffle)," Gordon said. "I was shocked. He just drove a great race."

Biffle, who until Sunday was Kurt Busch's teammate, drew praise from Kyle for the clean but intense racing.

"We never put a tire mark on each other," Kyle said. "I thought it was great racing. I hope it was as good on TV for the fans as it was in the driver's seat."