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.

After 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; he has denied that alcohol was involved.

Referring to his brother’s victory here in April, Kyle said, “It is a pleasure to carry on the Busch family’s name for both races this year.”

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

Unlike his younger brother, Kurt Busch made the 10-man Chase for the championship 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 lap 230 by staying on track when the leaders pitted. It was the second victory of Busch’s 41-race Cup career. He also won at California Speedway in September.