Frank Mir will tell you he has nothing left to prove. He’s a two-time heavyweight champion, he’s beaten the best strikers and the best grapplers at their own games. He beat one of the toughest ever — Big Nog, twice — once by TKO and once by submission. And he has the most wins by a heavyweight in UFC history. On the personal side, he has his own gym in Las Vegas, and is married with three children.

So what drives Mir? It’s hard to say — the spirit of competition, of constantly testing oneself against new and different opponents — is difficult to understand for those who have never felt it. Maybe Mir wants to cement his legacy further as one of the absolute best, a Hall-of-Famer. It’s possible he doesn’t have that burned-out feeling, that he needs to fight — he still wants to fight. Of course, all of this is speculation.

What is real is that Mir is challenging Junior dos Santos for the UFC heavyweight championship Saturday night at UFC 146. Dos Santos is considered by most to be the best pure striker, or boxer, if you will — since he rarely uses elbows, knees or kicks — in the UFC heavyweight division. His 60-second destruction of Cain Velasquez to win the title re-affirmed that he can end a fight in a blink against the best the division has to offer.

But Mir presents a real threat to dos Santos. He’s been in the game and worked hard enough to develop a formidable striking game — and he has the confidence to use those skills against anyone. Now add to that the most dangerous grappling in the HW division.

I see the fight going down similar to Mir’s fight with Cheick Kongo (and that is not to compare Kongo and dos Santos) — Mir will do what dos Santos will not expect: he will stand with him, and get a knock-down. Then Mir will swarm, and submit dos Santos. That is all.