LAS VEGAS — It was only two years ago that Matt Mitrione was a green rookie on The Ultimate Fighter. During that season, he was picked 13th out of 16 fighters, yet despite being the newest to the game, he’s now on the verge of being the most high profile of the bunch. At Saturday’s UFC 137, Mitrione will make a big leap in opponent level, facing the veteran Cheick Kongo. Mitrione has always been prized for his promise and athleticism, but given his late start in MMA (he was already over 30 when…