Dave Cowens wants to get back in the National Basketball Assocation, but at the moment his old mentor, Red Auerbach, is blocking the return of the former Boston Celtics star.

After sitting out the past two seasons, Cowens, 33, has made it known that he is available, and several NBA teams have inquired about his services for the coming season.

Phoenix, Portland and Milwaukee all have expressed interest. Auerbach is willing to negotiate with the Suns and the Trail Blazers, but, naturally, doesn't want Cowens to play for Milwaukee, one of Boston's chief rivals for the Eastern Conference championship.

"Everybody is waiting to hear from Red," Rich Gold, Cowens' attorney, said from his office in Boston. "Red is the stumbling block. Right now, he won't give Dave permission to talk with Milwaukee."

Cowens has a year remaining on a contract calling for a reported $450,000 and therefore still is the property of the Celtics. He has told friends he realizes there is no room on the Celtics' talent-laden front line for him, but that he is eager to play again.

Auerbach is on vacation until Tuesday, but before he left he explained his reluctance to deal with Milwaukee.

"Cowens, more than any other player, because he was a coach, should understand my position," the Celtics' president and general manager said. "He's not a free agent. He's a very valuable player and we're not going to let him go for nothing."

Don Nelson, Milwaukee's coach and director of player personnel, is a former teammate of Cowens' and is still a good friend of his. They have visited each other's camps in the Boston area and been together several times this summer, but officially, they cannot talk contract.

"I've seen Dave work out and he's in great shape," Nelson said. "Right now, I'm just waiting to hear from Red." The Bucks have been searching for a power forward and a backup to Bob Lanier at center and Cowens could fill both roles.

Milwaukee has offered either swing-man Junior Bridgeman, a seven-year veteran with a 14-point scoring average, or Brian Winters, a long-range shooting guard who lost his starting job to Sidney Moncrief last season, according to league sources.

Auerbach, Coach Bill Fitch and team owner Harry Mangurian have met and discussed what they want in return for Cowens. Phoenix has offered its first-round draft choice next year and, apparently, the Celtics have agreed. However, Cowens, who has a trade-approval clause in his contract, is hoping for an extension and a guarantee and is waiting to see if something can be worked out with Milwaukee.

General Manager Jerry Colangelo of Phoenix flew to Boston recently and watched Cowens work out at Boston College. Afterward, he proposed the deal.

"Everything's in limbo right now," Colangelo said. "We've made an offer and now its up to Boston.

"Cowens is such an unusual person, he shouldn't have any problem making a comeback. We're hoping he can play 20 to 24 minutes at either forward or center."

Portland made an early offer of guard Kelvin Ransey, but Cowens didn't show much interest in playing there and Ransey, a second-year guard, was traded to Dallas for Wayne Cooper and a first-round pick in 1985. Now it seems unlikely the Trail Blazers have enough to offer.

Cowens, who suffered a foot injury and missed 14 games, averaged 14.2 points and 8.1 rebounds in his last season. Despite persistent back problems, he had a career scoring average of 18.2 and was selected to play in the NBA All-Star Game seven times during his 10 years with the Celtics. He took over as coach early in the 1978-79 season, then was replaced by Fitch the following season.

John Havlicek, a former teammate who has watched Cowens work out, said the other day, "There is no question in my mind, Dave can play again."