It's hard enough to defeat the Los Angeles Lakers at Staples Center when a team suits up its entire roster.

The Portland Trail Blazers won't have everyone available on Sunday night.

After learning that star guard Brandon Roy will be out for at least a week, Portland will attempt to win just its third game in Los Angeles in eight seasons against the Lakers, who will go for their 15th straight victory at home.

Portland (20-13) dropped its last game, 92-77 to New Orleans on Friday, but suffered a more serious setback on Saturday as it learned that Roy, who has not played in the last two games, will be sidelined seven to 10 days with a strained right hamstring.

Roy, averaging a team-high 23.0 points, did not attend Saturday's practice to have an MRI on his left knee, which was surgically repaired in August. No major changes were found. He did not travel to Los Angeles for Sunday's game.

The Trail Blazers' other young star, Greg Oden, had just four points and four rebounds on Friday, snapping a string of two straight double-doubles. Against Los Angeles in the teams' first meeting this season, Oden injured his right foot and went scoreless with five boards in 13 minutes while making his NBA debut in a 96-76 loss on Oct. 28.

LaMarcus Aldridge posted his sixth double-double of the season on Friday with 13 points and 10 boards. He has scored 20 points or more in eight of Portland's last 12 games, averaging 19.0 points and 7.5 boards during the Trail Blazers' 6-6 stretch.

While Portland looks to rebound from its second-lowest scoring output of the season, Los Angeles is coming off its highest back-to-back scoring games this season.

The Lakers' 113-100 victory over Utah on Friday followed a 130-113 win over Golden State last Sunday.

Los Angeles leads the NBA in scoring, averaging 107.5 points.

Kobe Bryant scored 40 points against the Jazz - his 100th career 40-plus-point game - as the Lakers won their fifth straight. Bryant, third in the NBA in scoring with 26.8 points per game, is averaging 32.0 points, 5.8 boards and shooting 54.9 percent from the floor during the Lakers' winning streak.

In his last six home games against Portland, Bryant is averaging 38.2 points.

Trevor Ariza provided a big boost off the bench on Friday with 12 points and nine boards. He also had two of his career-high five steals in the final 2:22.

"I got in some passing lanes and I made some big plays," said Ariza, who leads the Lakers with 1.9 steals per game. "If we want to win, that's how we're going to do it, on the defensive end."

During their winning streak, the Lakers are holding opponents to 95.8 points per game and 45.0 percent shooting. Los Angeles is among the league leaders in field goal defense in 2008-09 at 44.0 percent.

In the opening night win against the Trail Blazers, Los Angeles held Portland to 34.5 percent from the field.

The Lakers have won four straight and 17 of their last 19 home games against Portland. The Trail Blazers' last win in Los Angeles was 112-108 on Feb. 21, 2007.