Frye lost all of his mobility. It improved during the course of the season. Hopefully, he got a LOT more back during the summer. But, even if he did, he's still not a "move their feet" kind of guy.
It's an odd year for him. His past pattern has been Good year > horrible year > Good year > horrible year. It's time for him to have a good year again.
Seriously though, I hope the best for him. I think he can be effective when given minutes, as long as all you really expect out of him is some outside shots.