His team is 6 games ahead of Harden and 14 ahead of Westbrook. He doesn't have the gaudy offensive stats of the other two, but he's the best perimeter defender in the league by a ridiculous margin.
That being said, I wouldn't be upset if it went to Harden either. I do ding Lebron, because somehow on a loaded team in a dreadful conference, his team is barely going to win 50 games. hes still probably the best player in the League, he just hasn't played like it this year.
So my ranking is
1a Westbrook
1b Leonard
1c Harden
2 Lebron
364 - Trey Lyles