Roy Tarpley's attempted comeback from a drug ban has failed, probably ending a troubled, turbulent NBA career.

The Dallas Mavericks center was banned by the NBA for the second time in just over four years Wednesday for using alcohol.Already banned once by the league for cocaine use, Tarpley violated the terms of his aftercare agreement by testing positive for alcohol consumption three times, most recently last week, the league said.

The violation nullified the contract that was to pay him $23 million the next five seasons.

Tarpley denies that he has been drinking, blaming the test results on a liquid cold medication that contains alcohol.

"We're all just dumbfounded," he told Dallas television station KDFW on Wednesday. "This is just a way for the Mavericks to get out of my contract."

His agent, George Andrews, did not return a phone call from The Associated Press on Wednesday night.

Tarpley could apply to the NBA and the players association for reinstatement.

"He's gone. I gave him my best shot," Dallas coach Dick Motta said. "I gave him as much advice as I could give anybody. It's a sad case, but he's a product of his own behavior. It's too bad, but Roy Tarpley screwed up big-time."

Tarpley, 31, who in 1988 won the NBA's sixth man award as the league's best reserve, was banned in October 1991, played two years in Greece and was reinstated by commissioner David Stern last fall.

Dallas owner Donald Carter welcomed Tarpley back to the team, giving him a six-year contract.

His contract also contained provisions for his aftercare program and could be voided if he was found to be using alcohol or drugs.

Mavericks president and general manager Norm Sonju said Carter indicated on Wednesday that Tarpley had blown his last chance with the Mavericks, with the owner saying, "This is the final chapter. The book is finished."'

In 55 games last season with the Mavericks, Tarpley averaged 12.6 points and 8.2 rebounds but clashed with Motta.

Tarpley began this season on the suspended list because of a pancreas ailment that bothered him throughout the summer.

The announcement that he had tested positive for alcohol came two days after another Mavericks player, Donald Hodge, was arrested on charges of possessing marijuana. The Mavericks and the league have taken no action because marijuana possession is not a violation of the NBA drug policy.