The Washington Bullets, who finally could wrap up the race for the league's best record tonight, got an unexpected gift yesterday: next year's NBA All-Star Game.

The All-Star contest was awarded to the Washington franchise after Boston, which had been scheduled to host it, pulled out because of problems dealing in part with possible renovation of Boston Garden and talk of a new suburban arena. The Celtics now will have the 1985 game, which originally had been given to the Bullets.

His will be the first time Capital Center has hosted the All-Star Game. The contest was played once in Baltimore, the former home of the franchise.

Next year's game will be played Feb. 3. The event has grown in importance lately within the league and has regularly attracted sellout crowds. The NBA also holds its mid-season league meetings at the site of the game.

There had been tal for months that Boston was trying to pull out of its commitment. The conversation increased with the club's unsettled ownership problems, sepcifically co-owner John Y. Brown's decision to run fo governor of Kentucky and his desire to sell his share of the team.

Among other reasons, Boston cited difficulties conforming with "standards relating to seating and facilities." A Celtic spokesman also mentioned "plans for partial renovation of Bostion Garden and some speculation that a new arena in the suburbs is a possibility."

The league's board of governors approved the switch, which Commisioner Larry O'Brien said made certain the game "will be held in an outstanding arena. I appreciate the concern of the Celtics and their desier to have this showcase attraction presented in the best-possible manner."

The Bullets, meanwhile, flew to Milwaukee yesterday to prepare for tonight's 8:05 game against the Bucks. Center Wes Unseld, who missed Sunday's contest against Denver with the flu, did not go with the team but could join the Bullets today if he feels better.

Washington has only five contests left and, because of league tie-breaker rules, has reduced its magic number to two in the race with Seattle for the best record.

Any combination of Bullet wins and Seattle losses adding up to two would guarantee Washington a tie for the No. 1 mark. If that happens, the Bullets would gain the home-court advantage in every series during the playoffs because they have a better record than Seattle within their respective conference.

The conference record is the second tie breaker. The first-head-to-head competition-is moot because the clubs split their season series.

Seattle begins a seasion-ending four-game road trip by playing at Portland tonight. The Trail Blazers, the hottest team in the league, also are the toughest home-court club. If the Bullets beat Milwaukee and Seattle loses to Portland, the best-record race would be over.

Washington, however, still has a magic number of three to guarantee sole possession of the $50,000 that goes with the No. 1 record.