PORTLAND, Ore. (AP) – Tony Allen had 22 points and eight rebounds and the Boston Celtics ended their six-game slide with an 89-81 win over the Portland Trail Blazers on Monday night.

Rookie Brandon Roy had 18 points to lead the Blazers, who let the Celtics build a big lead during a cold fourth quarter.

Neither team shot well, perhaps because of the return of the leather ball.

Ryan Gomes had 18 points and 10 rebounds for the Celtics, who concluded a five-game road trip. Al Jefferson added 14 points and 11 rebounds and Wally Szczerbiak had 15 points.

Ime Udoka and Martell Webster had 11 points apiece for the Blazers. Zach Randolph finished with nine points and 10 rebounds on a 4-for-11 shooting night. Portland has lost five of its last six games.

Minnesota and Charlotte played in the only other NBA game Monday, when the leather ball made its return.

After numerous complaints about the synthetic ball introduced at the beginning of the season, the league decided to switch back to the old ball.

Boston coach Doc Rivers had complained that the new ball gave Portland an advantage because the Celtics played Sunday night with the composite ball and wouldn’t be able to have a shootaround between games to get acclimated to the leather one.

Neither team played well, but Portland was more lethargic, having last played Saturday at Utah.

Portland shot better than 60 percent in the first quarter, but finished 28-of-72 from the field (38.9 percent).

The Celtics shot 43 percent from the field.

Portland led by as many as eight points in the first half, taking a 31-23 lead early in the second quarter. The Celtics whittled the lead down in the second as the Blazers went cold. Szczerbiak hit two free throws and Delonte West hit a running jumper to tie it 44-all at halftime.

Boston led 68-67 at the end of the third on Gerald Green’s rebound and putback.

The Blazers suffered through a 9:46 stretch in the fourth in which they went 0-for-11 from the field with five turnovers and just six points. Szczerbiak scored to make it 76-72 and Allen had back-to-back baskets, the last one a 3-pointer, to stretch the lead to nine.

Webster hit his third 3-pointer of the night to get Portland within 83-79 at 1:26. But Szczerbiak had a steal and layup, and West hit two free throws.

Sebastian Telfair had an uneventful return to Portland, with two points and three assists in 17 minutes for the Celtics. Telfair played two seasons for the Blazers after being drafted out of Abraham Lincoln High School in New York in 2004, but was traded to Boston on draft day last June. The 6-foot point guard entered the game averaging 8.7 points and 4.1 assists for the Celtics, but was replaced in the starting lineup last week by West.

Notes: Boston has beaten the Blazers four straight times. … Jefferson had his 11th double-double. … The Celtics had 50 points in the paint to Portland’s 28.