"Obviously, I'm optimistic about playing," he said Thursday. "I always am. Today was a good day.
"The progress thus far since last Sunday has been really good. I feel it's a lot further than I expected. It feels a lot better than I thought it would feel and I'm just happy where it is right now. Today was a very positive day and we'll just see what happens tomorrow."
Bush took a helmet to his knee midway through the second quarter of last week's 25-21 loss in Arizona. He came back for a few plays after the hit but wasn't himself and sat out the rest of the way.
Without Bush, the Lions struggled to only 90 yards of offense in the second half in Arizona.
"He's improving," head coach Jim Schwartz said. "We'll see where he gets to by the time we get to the game. We have a long time between now and the game. If he can be ready and if he can play then he's tough enough to do it.
"You know I don't put timetables on guys when it comes to having to practice on a certain day. We have had a lot of players that have gotten back to practice and didn't play.
Bush said he wants to get back on the practice field Friday to test the knee out for himself.
"It's going to come down to what I can show them on the field," Bush said. "It's not going to be about what I say. I can say a whole lot of things, but if I can't show it on the field, I shouldn't be on the field on Sunday."
Bush did not practice Wednesday or Thursday.
He said playing Sunday will be a collective decision between himself, the doctors, trainers and coaches.
"If it were up to me, I'd just say, ‘yeah, I can play right now,'" Bush said. "That's the competitive side.
"That's kind of what happened this last game. When I got injured, I probably should have stayed out of the game, but coaches asked me and I thought I could go and fight through the pain and I couldn't and it showed on the field."