And that includes Junior dos Santos, who he's "not completely sold on" just yet.
Apparently, though, it wouldn't make much of a difference in his opinion.
Velasquez, despite having not even reached double digits in terms of career fights (9-0), is as well-rounded as they come. His combination of striking and wrestling will be tough for any 265-pounder to handle.
But that's not what truly makes him so deadly.
Not according to Mir, who says his biggest advantage is that he excels at the one aspect that is the absolute bane of the heavyweight division's entire existence.
"I'm still not completely sold on dos Santos. (He hasn't seen the UFC 131 fight between JDS/Carwin). I don't know how well-rounded he is. Velasquez right now, though, I think is a hard match-up for everybody," Mir told ESPN (via Fight Opinion). I think he posses the one tool that is every heavyweight's Achilles heel and that's his cardio. It's amazing that he has cardio on the same level as most Welterweights that are at the top of their cardio game. He's shown to be extremely well-rounded as far as hands, takedowns. He threw Brock Lesnar around like a rag doll, I couldn't believe it, I mean he out-struck him obviously but he picked him up and threw him down and I was blown away by that. Also, Brock with all that size and power couldn't even hold him down once he had taken him down. So, right now, I'm pretty much if you tell me Cain Velasquez and anybody to name on the other end of that roster, I would bet on Cain Velasquez."
Ah, yes. Cardiovascular conditioning.
Velasquez, perhaps the least imposing fighter in the entire division, may not have the impressive bulging muscles like many other heavyweight hitters, but he's just as effective.
And his smaller frame is much easier to get oxygen to.
Maybe it's just Mir lamenting the fact that his cardio has never quite been up to snuff, although he's improved drastically from his earlier days.
Or it could be that Cain, despite not possessing the biggest body of work, truly is the greatest heavyweight in the sport.
When he takes on dos Santos for the title later this year, Frank Mir's money will be on Velasquez. Who will you put your money on?