That's what Sergio Non(USA Today) thinks:
Here's all you need to know about the state of mixed martial arts' middleweight division: its best guy outside the Ultimate Fighting Championship is leaving the weight class and its best guy, period, plans to quit the sport entirely next year.
The man who might be best equipped to challenge Silva currently competes outside UFC's boundaries.
Only 23 years old, Gegard Mousasi already has established himself as one of the top middleweight competitors. He capped a 6-0 run this year with an impressive performance in the Dream Middleweight Grand Prix. Among his victims were Denis Kang, a star from Pride Fighting Championships; Melvin Manhoef, probably the hardest hitter in the sport; and Ronaldo "Jacare" de Souza, the most accomplished grappler among MMA middleweights — and none of them made it past four minutes. Even Silva hasn't faced that level of opposition, both in terms of quantity and quality.
As you can see in my fighter rankings, Mousasi isn't even in my top ten at the moment. That will probably change when I update them at the end of the month, then again it may not since Mousasi is moving up to 205. Mousasi's run in the DREAM GP was impressive, but to say that Anderson Silva hasn't faced the same if not better level of competition is something I can't agree on. Mousasi's opponents in the DREAM GP were very one dimensional fighters(except Kang) with most reputable sites not even ranking these guys in the MW top ten.
Whereas Anderson Silva has done nothing but beat and finish 3 MW fighters that most people have at or near top 5 in the middleweight division. I also don't think I agree with Mousasi being the best MW fighter outside of the UFC either. I'm pretty sure that Paulo Filho, Frank Trigg, Matt Lindland, and possibly a couple of other fighters would have something to say about that. I do think Mousasi has skills, but I'm not ready to hop on that bandwagon just yet. He needs a couple of wins over more quality competition before he wins me over completely. Who would you list as the best MW fighter outside of the UFC?
*Yes, I know Filho is moving to the UFC.