Derrick Rose injured his right knee Friday night and the Chicago Bulls star, who sat out last season following surgery on his other knee, did not return during a 98-95 loss to the streaking Portland Trail Blazers.
Wesley Matthews had a season-high 28 points and Damian Lillard added 20 to help the Trail Blazers run their winning streak to nine games.
Rose led the Bulls with 20 points, five rebounds and three assists but was assisted to the locker room with 3:20 remaining in the third quarter. The 2011 NBA MVP tore the anterior cruciate ligament in his left knee during the 2012 playoffs and missed last season while recovering from surgery.
Carlos Boozer had 16 points and Luol Deng added 15 points and 14 rebounds for Chicago.