Thompson was injured after he faked a shot and Ariza knocked him to the floor with a knee to the head in the fourth quarter of Game 5 of the Western Conference finals Wednesday night.
Thompson received stitches in his right ear and passed a concussion test during the game that would have allowed him to return. The Warriors did not need him as they won the game 104-90 to clinch the series.
The Warriors said Thompson developed concussion symptoms after the game and will be evaluated by the medical staff. Thompson must pass the concussion protocol before he can return to play.
The NBA Finals start June 4.