"It's always sad to see some of your guys go down," said Webster, who was coming off a 22-point game. "But that's when other guys step to the plate. Coach always tells us that when your name is called, you have to be ready."
Jarrett Jack added 17 points for the Blazers, who shot 49.4 percent despite Roy leaving with a strained right groin on the last play of the first quarter. Portland was already without LaMarcus Aldridge, the team's second-leading scorer who sprained an ankle Monday against Seattle.
With Portland short-handed, Webster stepped in and hit nine of 14 shots, including four 3-pointers. The third-year forward entered averaging 10.8 points and has started most of the season, but hasn't been a focal point of the Blazers' offense.
The game was also about redemption for the Blazers, who suffered through a lackluster 13-point loss to Seattle the night before.
"This was a huge win for us," said Joel Przybilla, who had 17 rebounds. "I think that was one of our best wins of the year. It was the fourth game in five nights, we played horrible last night and two of our guys go down. Everyone stepped up."
Antonio Daniels had 14 points and eight assists for the Wizards, who had won six of their last seven. Leading scorer Antawn Jamison struggled, with nine points and eight rebounds on just 3-of-13 shooting. Washington shot just 35.8 percent as a team and never led.
"It was the story of two teams," Wizards coach Eddie Jordan said. "One team could shoot straight, the other team couldn't."
Arenas, who has missed all but the Wizards' first eight games, hasn't been cleared by team doctors despite participating in the team shootaround before Washington's game Sunday against Detroit.
Portland shot 68 percent in the first quarter and led by as many as 11 before Roy went down.
Roy, averaging 19.5 points and 5.8 assists per game, had six points, four rebounds and four assists before leaving. The All-Star guard was attempting to block Butler's 3-pointer before the first-quarter buzzer, but he landed awkwardly and crumpled to the floor.
After being taken to the Blazers' locker room, Roy returned briefly in the second quarter, but was limping noticeably and left for good after less than two minutes.
Coach Nate McMillan said Roy would be evaluated Wednesday to determine the extent of his injury, but he wasn't optimistic.
"That (injury) can sit you down for a month," he said.
Portland struggled briefly after Roy left, missing seven of nine shots to start the second quarter.
The Wizards cut the lead to 33-32 on Roger Mason's 3-pointer. With a 42-39 lead, Portland went on a 13-4 run that Outlaw and Jack capped with back-to-back 3-pointers.
The Wizards never contended in the second half, continuing to miss shots while Portland pushed the lead to as high as 24 points.
- F Aldridge was a game-time scratch for the Blazers after spraining his ankle in the third quarter Monday at Seattle. He was averaging 24.0 points in his last full nine games.
- Portland, the fourth-worst rebounding team in the league, outrebounded the Wizards 55-36.