Ellis was diagnosed Tuesday with a strained lower back. He underwent X-rays and a CT scan after falling awkwardly to the floor with 1:22 remaining in the Warriors' 109-102 win over the Raptors, in which Ellis scored 28 points.
He remained down for several minutes before being helped up, then walked slowly to the locker room.
Ellis is averaging 27.9 points for Golden State (5-2), which plays at the Knicks on Wednesday. He is listed as day to day.