With the cast coming off Thursday morning, Harris said he wouldn't know if he could play in the Spartans' game against Oakland on Saturday.
"We will see how things go (Thursday)," he said. "I wanna play on Saturday. I don't know it's going to be when I get it out so we will go from there. …
"It's on me. It's precautionary. They just put me in a cast since we had this time so I couldn't take it out or anything and so I get all the rest I needed."
The sophomore had been held out of practices leading up to MSU's loss to North Carolina, but tweaked it early in the second half.
"I walked it off and came back in, but it actually was feeling really good before that in the first half," he said. "I just tweaked it a little bit and it wasn't really right."
"This is what I want," he said. "This is what I came here for. It's a challenge, but I want the challenge. That's what I came here for."
Valentine, who lives with Harris, said Harris is pretty mad about the injury setback but understands its part of the game.
"He's good at that, not being all down," Valentine said. "He's good at saying forget this, I'm going to work even harder to get back."
Harris said he will come back when he feels comfortable with playing on his ankle.
"I'm going to come back when I feel like I'm comfortable enough to play," he said. "I'm not worried about it lingering or anything. Just when I feel like it's right."
Michigan State plays Oakland at The Palace of Auburn Hills on Saturday.