Kevin Garnett, Paul Pierce, Ray Allen and Doc Rivers can boast they accomplished something Bill Russell, Larry Bird, Bob Cousy and Red Auerbach never did when their Boston Celtics teams were ruling the NBA:

Open a season 21-2.

Allen and Pierce scored 22 points apiece, Garnett nearly had a triple-double, and Boston beat host Washington last night, 122-88, for a 13th consecutive victory and the best start in the storied franchise's history.

The Celtics also own their longest winning streak since a 14-game run in 1985-86.

Garnett finished with 11 points, 12 rebounds and seven assists in three quarters.

Caron Butler scored 19 points for the last-place Wizards, who matched their franchise's slowest start, dropping to 4-16 for the first time since 1966-67.

The Celtics knew what they were playing for. Twice before, including last season, Boston went 20-2 before losing Game No. 23.

"It's always great to be part of a team that's potentially mentioned as one of the franchise's best," Allen said.

In another game:

* At Dallas, Dirk Nowitzki hit a key three-pointer in the final 30 seconds and finished with 23 points to help the Mavericks beat trade-depleted Charlotte, 95-90. Emeka Okafor had a season-high 27 points and 17 rebounds, and Raymond Felton added 16 points for Charlotte.

Raja Bell, Boris Diaw and Sean Singletary are expected to make their Charlotte Bobcats debuts tomorrow night against Detroit, coach Larry Brown said yesterday. The Suns sent Bell, Diaw and Singletary to Charlotte for Jason Richardson, Jared Dudley and a 2010 second-round draft pick.

Noteworthy

* Houston forward Ron Artest will sit out the next two games with a sprained right ankle.

* Cavaliers center Zydrunas Ilgauskas is expected to miss at least two games after spraining his left ankle in Cleveland's win over the Sixers on Wednesday.

* Oklahoma City forward Chris Wilcox is expected to miss 10 to 14 days after dislocating his left ring finger. *