LAS VEGAS — The gap between Cain Velasquez and Junior dos Santos is fairly slim. The gap between Velasquez, dos Santos and the rest of the heavyweights? It’s more like a canyon. There are a lot of big men in the world, but they are the only two in their class. That might not be the case if Daniel Cormier wasn’t insistent on moving to 205 (he told reporters on Saturday night he was definitely going down). That might not be the case if Jon Jones soon follows through on a stated intention to move up to heavyweight. But for right now, Velasquez and dos Santos are the 1A and 1B, the king and the the crown-chaser, with those labels perfectly interchangeable. That was proven again on Saturday night, when both emerged victorious from their respective bouts at UFC 160. In a conventional sense, the wins didn’t tell us anything new. Both, after all, were sizable favorites to win. But looking deeper, past the numbers and the opponents, both Velasquez and dos Santos faced something new.For Velasquez, he was guarding against complacency. The men who have gotten to the top in mixed martial arts will tell you it’s harder to stay there than it is to get there in the first place. Velasquez had to do it against an opponent that he had already starched. If he was ever going to have a moment of laziness or disinterest, this was it. Instead, he beat Antonio Silva even faster than he did the first time. It took just 81 seconds. Think about this for a second: over two fights, Silva has only been able to land five combined strikes. This is a man who has knocked out Alistair Overeem and finished Fedor Emelianenko. Silva has been in or around the top 10 for about three years now, and he has been positively overwhelmed and outclassed by Velasquez. dos Santos was fighting a possible loss of confidence. Facing the surging and powerful Mark Hunt, dos Santos was competing for the first time since losing the championship to Velasquez. dos Santos didn’t just win. The Brazilian bombed Hunt, cracked through his seemingly impenetrable chin, and closed him out with a spinning wheel kick. Yes, a 6-foot-4, 240-pound man threw and landed a spinning wheel kick. It was, he said, the first time he has ever tried it in a fight, and of course, he drilled it. That is a technique rarely thrown by heavyweights, but dos Santos is gifted and athletic, and most of all, he’s fearless. That’s not a strike you throw if you have any risk-aversion, and he proved he was willing to go into the lion’s den with the way he fought Hunt. dos Santos out-landed the Super Somoan in every round. It went 20-5 in the first, 35-20 in the second, and 25-9 in the third. It was all speed, smarts and power.Think about this: in Hunt’s entire MMA career, he’d been knocked down only once. dos Santos did it twice in less than 15 minutes. That’s the thing about Velasquez and dos Santos: they do things other simply can’t, because they’re a level above.There are other names in the division, of course. When we last saw Fabricio Werdum, he looked as good as ever, but he’s spent an inordinate amount of time on the sidelines, and he’ll soon be 36 years old. Antonio Rodrigo Nogueira is probably too battle-weary at this point of his career. Frank Mir has fallen from the contending elite. Newly signed Josh Barnett? He might make for an interesting fight, but he doesn’t have the wrestling to slow down Velasquez, and he doesn’t have the power to firefight with dos Santos. Overeem has a long climb back into the division’s top five, and his gas tank is a major question mark against either conditioning freak.There aren’t a whole lot of other names worth mentioning. There are no young prospects tearing it up and demanding attention. The top of the division is Velasquez and dos Santos. Everyone else is fighting for No. 3.These two are meant to be together, a pairing with meaning. Later this year, when they meet up for the third time, the title could change, but even if it does, the shakeup will be minor. Velasquez and dos Santos aren’t going anywhere. They’re far and away the division’s best. Even in a sport that builds and rips down new contenders in a hurry, that’s unlikely to change. It’s going to be a long wait for a heavyweight changing of the guard. This is their division. As of now, the gap between them and everyone else is only widening, promising the continuation of the sport’s most respectfully ferocious rivalry.