Washington Bullets Coach Dick Motta said yesterday he believes guard Phil Chenier must have a back operation before he again can play basketball.

Motta also said he would like to have free-agent center Marvin Webster play for the Bullets.

"I'm pretty sure from talking with Chenier's docter and others close to him that he will need surgery," Motta said at St. Mary's College, where he was helping give a clinic at Bullet center Wes Unseld's basketball camp.

Chenier, who missed most of last season with a degenerative disc problem, thus far has been unable to improve his condition through rest and therapy.

"Chenier's status will have great bearing on Roger Phegley's chances of making the team," added Motta. The Bullets made the 6-foot 7 Phegley, from Bradley, their first pick in the June college draft. A big guard was the teams's first priority following last season's playoffs against San Antonio and Seattle, when Washington was victimized by its opponents' tall backcourt men.

Webster, a 7-foot shot-blocker, left Seattle following the SuperSonics' seven-game defeat by Washington for the 1977-78 NBA title.

"I know that (Bullet General Manager) Bob Ferry has made inquiries about Webster," Motta disclosed. "With Joe Pace gone, this is a good year for a center to catch on with us."

Third-string center Pace, disenchanted by his lack of playing time the past two seasons, signed as a free agent with the Boston Celtics last week. Center Dave Corzine of DePaul, the Bullets' second draft choice, is still unsigned.

However, any newcomer will face a struggle in making a team that, according to Motta, should improve.

"They're young and there is no reason they cannot get better," said Motta.

Motta foresees no changes in the Bullets style of play. "The results prove what we're doing is real good," he said.

"One thing I'm going to have to do is to find more minutes for Greg Ballard. He's got to play more and will, even if I have to take minutes away from (Bob) Dandridge, (Elvin) Hayes and Wes.

"I think that history may show that we have the best set of forwarls, from one through four (Hayes, Dandridge, Mitch Kupchak and Ballard) that ever played together."

Motta said he is counting on the return of Unseld. The most valubale player in the final playoff series said at the end of the season that it was 50-50 as to whether he would be back for another season.Unseld recently said he would "most likely" be back.

With one year remaining on his original three-year contract, Motta has no plans to leave. "I've changed my license plates, bought a home and enrolled my kids in school" he said. "I did not come here to the Washington area to work just one year. I'd like to plant roots here."

The Bullet coach has a lunch date at noon today at the Touchdown Club's salute to the Bullets. Next month, Sept. 4-11, the team will play in Israel. Preseason training camp opens Sept. 13.