Naka is playing terrific chess this year. He seems a bit more patient and confident. Like Magus and like Topalov, Naka is always looking for some way to win, even in the driest position.
Yeah, and he's not playing dubiously to do so, like Carlsen. I think it's hard (read: impossible) to beat a player that doesn't make mistakes, and Nakamura has played (save for the loss against Anand) virtually error-free chess.
Nakamura has only lost one classical game this year, and it was not because of over-pressing. In his only game against Carlsen this year, he drew comfortably, though Carlsen still made him work for it. And, he may have the highest 2015 performance rating (Apparently, Carlsen's performance rating for the year was 2885 and Nakamura's was 2840 before Norway, which makes me think Nakamura's is higher now since Carlsen had a well-known disaster in Norway). How about that?