I'll be honest. After watching Yan's fights with Faber, Aldo and Sterling, I slept on him a little bit. I appreciated his hand speed, but I was never a big fan of how stationary and defensive he was at times. During his fight with Sandy though, I was completely blown away. The guy's head movement, footwork, and counters were on point, and his ability to piece together fast combinations was on full display. The spinning backfists were things of beauty too. They may look impractical, but with the proper setups, you can land them clean.
I usually have a hard time deciding who the best fighter in the UFC is, because a lot of them do not have fast hands, fast footwork, solid defense, consistent counters and consistent pressure all at the same time. I jumped from person to person. First, it was Dominick Cruz. After learning more about what worked in fighting, Dustin Poirier became my favorite. Then, I went over to Volkanovski.
But finally, I can (personally) say that Petr "No Mercy" Yan is the best fighter in the UFC right now. He's like Canelo if he went into MMA; his guard is high, has good head movement to match it, and counters you hard the moment you decide to throw anything. He just operates so smoothly with his hands, and when he makes you afraid of them, he literally goes for pretty much anything he can think of on the spot, and he pulls it off on a stupendously high level (e.g. body kicks, spinning attacks of all kinds, taking the back, etc.).
Yan vs Sandhagen 3.mp4
Yan vs Sandhagen 5.mp4
Yan vs Sandhagen 6.mp4
Yan vs Sandhagen 8.mp4