The All-Star landed awkwardly in the closing stages of the 131-123 victory over the Indiana Pacers on Tuesday night and he was immediately forced to come out of the game.
Despite not yet being ruled out of the game in Boston, Thompson admits that he still does not feel fully fit after a couple of days off.
"It's not feeling great, but it's not feeling bad," Thompson told reporters after watching his teammates practise on Thursday. "It's like somewhere in between. It's like 60% - nah, 70.
"I'm optimistic about life and Friday, and yeah I'm optimistic. I think if I have a good shootaround, I'll play."
Golden State are already without starting small forward Harrison Barnes due to an ankle injury.