Twelve games into the season, Dallas Mavericks Coach Dick Motta decided to put his five best players on the floor and go with them. The results have been mixed.

Dallas has a respectable (for it) 12-17 record going into tonight's game against the Washington Bullets at Capital Centre at 8:05, but has lost eight of its last nine games.

Motta's "best" include center Pat Cummings, a natural forward; Mark Aguirre and Jay Vincent, two natural small forwards; and former Maryland player Brad Davis and Rolando Blackman at guard.

Those five are all in double scoring figures, but defensively and on the boards the Mavericks are having problems. And the team has little depth. The starters average 85 points a game and the reserves only 27, the lowest such ratio in the NBA.

The Bullets, in contrast, with Frank Johnson and Don Collins out with injuries, are getting only 53 points from their starters, but 35 a game from their reserves.

The Mavericks broke with tradition in the offseason and traded one of their many future No. 1 future draft choices and center Wayne Cooper to Portland for point guard Kelvin Ransey. Ransey hasn't been able to beat out Davis. He didn't play at all in three of Dallas' last five games, and in the last 11 games he made only 20 of 60 shots.

Davis, meanwhile, has emerged as a steady point guard. He is averaging 12.2 points and has the best shooting percentage (57) of any guard in the NBA. He also is averaging 6.2 assists per game.

The biggest surprise for the Mavericks has been Cummings, acquired from Milwaukee for a second-round draft choice. Because of his scoring ability and mobility, Cummings, 6 feet 9, beat out Kurt Nimphius and Scott Lloyd.

Spencer Haywood is still bothered by an injury to his right eye and didn't practice yesterday. His status for tonight's game is uncertain . . . Johnson began working out on his own Sunday and is expected to start practicing with the team on Monday.