Mccully is the dark haired guy with a mullet who trains with Tito's camp, yes? If he's the one I'm thinking of then his cardio is not where Brocks is at all. Nor is his strength level. I don't think he's a tomato can either, he's a decent fighter who could be a name much further down the road.
This is probably what Brock needs to establish himself in the UFC. He really needs to beat a couple of lower level fighters and work his way further up the ladder. To continue pitting him against top level fighters when his experience level simply isn't there would be a mistake. The guy really does have the attitude and the aptitude to be the best, I'm sure everyone can see that. I say it's good to let him move up the ladder at a regular pace instead of throwing him in with the lions over and over again.