Rolando Blackman's two free throws with eight seconds left capped a rally that offset Larry Bird's 50 points, carrying the Dallas Mavericks to a 116-115 triumph last night in Dallas, their first victory ever over the Boston Celtics.

The Mavericks were 0-11 against the Celtics since they joined the league in 1980. They overcame a 13-point deficit with less than five minutes left in the game.

"No big deal," said Bird. "I should have had 54. If you play a team enough, losing is finally going to happen. The shots were there for me, and I just took them."

Bird scored 17 points in the third quarter, and the Celtics took a 104-91 lead in the fourth. Brad Davis put Dallas ahead, 111-110, with 43 seconds to play with a pair of free throws. Then Dale Ellis hit a three-point shot with 16 seconds to go for a 114-110 lead.

Bird hit a three-point shot. Then Blackman, who had 32 points for Dallas, was fouled and made two free throws. After a timeout, Bird hit a layup with four seconds left.

For the Mavericks, who were without Mark Aguirre, Davis scored 18 points and Sam Perkins added 24. Dennis Johnson scored 19 points for the Celtics, who lost their second game in a row. Suns 120, Pistons 109

Larry Nance tied his career high with 44 points as Phoenix ended Detroit's 15-game home winning streak.

The Suns, who had lost four straight, had 19 points from reserve forward Mike Sanders. Kelly Tripucka scored 30 for the Pistons. SuperSonics 111, Warriors 108

Jack Sikma drove for a three-point play with four seconds remaining, giving Seattle the victory over Golden State in Oakland.

Xavier McDaniel had 26 points for Seattle. Joe Barry Carroll and Purvis Short scored 22 each for Golden State.