Lillard, who had averaged 37.66 points across his past three games heading into Wednesday's game, limped out with approximately five minutes left in the third quarter.
The Blazers point guard appeared to injure his calf while shooting a three-pointer to cut the margin to 77-70, before limping out after the next offensive play.
Portland confirmed that Lillard had suffered a right calf strain, but the 32-year-old downplayed the severity of the issue after the game.
"It wasn't nothing that I was overly concerned with," Lillard told reporters. "I just know that it wouldn't make sense to try and push through it in the fifth game of the season.
"Honestly if this was a playoff game, I would have played. It would have been tight and uncomfortable, but I would have played. If that gives you any indication of how concerned I am now or would have been."
With Lillard forced out, the Blazers suffered their first loss of the season. Lillard finished the game with 22 points from 26 minutes.
Lillard is averaging 33.3 points, 5.5 rebounds, 5.3 assists and 0.8 steals per game through five games this season.