I think Brock could take it. He's a legitimate NCAA champion with incredible, strength size and agility. Real wrestlers of that caliber have an extraordinary work ethic, and if he's trained properly I could see him being a serious contender in a short period of time.
A win would make him an immediate player and a loss could still legitimize him as a real fighter especially against Mir. (As long as it's not a squash [to steal a pro wrestling term
])