PORTLAND, Ore. - A big Boston win had Celtics coach Doc Rivers changing his tune about the return of the leather ball. Tony Allen had 22 points and eight rebounds and the 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 went cold in the fourth quarter and let the Celtics build a big lead.

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

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

After Monday's game, he was just happy to have the win.

"I could care less about the ball," Rivers. "I did think they might have an advantage with it, but at the end of the day, when the tap goes up everybody's playing with the same ball, just like we were yesterday."

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 added 10 rebounds and nine points on 4-for-11 shooting. Portland has lost five of its last six games.

"It was a defensive win," Rivers said. "Ryan Gomes was phenomenal. He obviously had a lot of help, but he was just denying Zach the ball and trapping him on the catch. I thought our guys executed the game plan and stayed with it ¡ª that got us the win."

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.

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

"This time of year we need to be focused and dialed in ... we need to establish ourselves both on offense and defense," Webster said.

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 for the game.

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 when the Blazers went cold in the second. 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.

"We are not playing hard," Portland coach Nate McMillan said. "If you don't compete hard enough in this league you're not going to beat anybody."

Webster hit his third 3-pointer of the night to get Portland within 83-79 at 1:26. But Szczerbiak made 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.