Mavericks point guard Derek Fisher left Dallas' game against the Philadelphia 76ers on Tuesday night with a strained right knee.
Fisher had his shot blocked by Evan Turner and went down to the floor holding his knee after he landed. He walked slowly to locker room with 6:50 left in the first quarter.
The team said Fisher's return to the game is doubtful.
Dallas coach Rick Carlisle told reporters before the game that Fisher wasn't going to play because of the flu, but the 17th year veteran started before his early exit.
Fisher signed as a free agent with the Mavericks on Nov. 29. The 17th-year guard came in averaging 9.4 points and 3.9 assists in eight games this season.