The Lakers were trailing 54-45 with 2:21 left in the second quarter when Howard grabbed his shoulder, asking Coach Mike D'Antoni to substitute for him.
Howard went to the locker room and did not return for the second half . He will be reevaluated on Thursday when the Lakers return to Los Angeles. Pau Gasol started the third quarter at center.
The Lakers lost Howard for three games earlier in the month after he injured his shoulder against the Clippers on Jan. 4. He tried to play through the pain but aggravated the injury two days later against the Denver Nuggets. The Lakers lost all three games without Howard.
The team initially announced Howard had a torn labrum but the center later said that the labrum itself was still intact but it had ripped away from the bone.
Howard declared earlier in the day that the Lakers' season would start tonight against the Grizzlies. If so, the new season strikingly resembles the old one, marked by injuries and defensive lapses.