I'd say Greg Monroe. Lin+ Anderson should be in the running, but I feel like with them it's more about opportunity than actual improvement. Same with Bradley (but not even near the Lin/Anderson level). I can't say he's a significantly better shooter, passer, dribbler, or defender than last season. He was a top level defender then , and still is. He was a suspect shooter, passer, dribbler last year, and still is. You don't give MIP to a guy for cutting well lol.
If you throw out small sample size, I'd say there's a strong case for Byron Mullens. He looked like he was on his way out of the league last year+ earlier this year. Recently he's looked like a developing all star.