CHARLOTTE, N.C. -- If the NASCAR community had one universal wish for Kyle Busch on his 21st birthday, it probably would be for him to start behaving like an adult.

Busch, one of the youngest drivers in the Nextel Cup series, has been under constant criticism this season for reckless or immature behavior. He's twice tangled with series champion Tony Stewart, wrecked race leader Michel Jourdain Jr. in Mexico City, took the brunt of the blame for aggressive driving in Daytona and was ticketed for reckless driving in Richmond.

Most recently, he gave Casey Mears a retaliatory bump under the red flag at Phoenix that earned him a five-lap penalty and a severe tongue-lashing from NASCAR president Mike Helton.

"The guy is really fast and he's got a lot of talent, but he really does a lot of stupid stuff -- and that's across the board, that feeling throughout the garage," Mears said. "When he grows up, he's going to be a real good race car driver."

Busch's rivals eagerly await that day. He celebrated his 21st birthday on Tuesday and is rapidly closing in on a time when he won't be able to shrug off his errors as youthful mistakes.

For now, much of what he's done can be attributed to immaturity.

"You've got to remember how old he is," said four-time series champion Jeff Gordon, Busch's teammate at Hendrick Motorsports. "He's got pressure on him. He's got a tremendous amount of talent. He has a great team."

It doesn't help that he's the kid brother of Kurt Busch, who had more than his share of missteps in his first four Nextel Cup seasons. During that time, Kurt Busch became one of the most disliked drivers in NASCAR -- both in the garage and the grandstands.

It's possible that Kyle is paying the price for some of his brother's sins. He's been cut very little slack since graduating to the Cup series last season, and the criticism directed at him has seemed harsher than what's leveled at the rest of the young drivers.

"He's definitely guilty by association," Kurt Busch said. "But he's also young and an aggressive racer who likes to race hard."