I've read that he felt underappreciated and under-used in Phoenix, but it could be that he just hasn't come to grips with how much his physical skills have slipped in his 10 year career.
He can still score double-digits and help the Knicks in many areas, if he accepts the role they give him.
I'm assuming he will come off the bench, which instantly gives the Knicks some extra scoring firepower and experience there.