Gotta agree with the guy who said Khabib. He was just some random foreigner with a confusing name before this year, now he's on the edge of contention. Connor is also a good pick. Those guys moved their names up several levels.
I can't call Pettis, Weidman, and Gus breakouts. They were already pretty big before this year. If Weidman beats Silva again though, then maybe you could say he moved up multiple levels to become a breakout.