Wesley Johnson suffered a strained right hip flexor on Sunday night during the Lakers' game against the Indiana Pacers at Staples Center.
The 6-foot-7 forward will undergo an MRI exam on Monday, staying behind as the Lakers travel to Portland to play the Trail Blazers.
Heading into Sunday's game against the Pacers, Johnson had played in all 33 of the Lakers' games, averaging 9.7 points and 3.8 rebounds.
Coach Byron Scott indicated Sunday that Kobe Bryant would miss Monday's game to rest, putting the Lakers down two regular starters against Portland.
Wayne Ellington is expected to start for Bryant, and perhaps reserve swingman Nick Young will get the nod for Johnson.
Portland is one of the top teams in the Western Conference at 26-8.