While in some ways UFC 137 will go down as a lackluster event, it will also be remembered as the last time we may have seen two legends of the sport in action.
Mirko Cro Cop suffered yet another TKO loss in the third round of his bout against Nelson. After the bout, he announced that win or lose, he had already decided to walk away from the cage.
Penn, on the other hand, was very effective early in his bout against Diaz, only to fade as the rounds went on. Diaz would go on to put a beating on Penn en route of winning via unanimous decision.
Following the bout, Penn stated "I can't let my children see me like this," and said that he was done with the sport (via SB Nation).
In other action, Cheick Kongo derailed another heavyweight's rise to the top as he handed Matt Mitrione his first professional defeat. Hatsu Hioki made a lackluster UFC debut by winning a split decision over George Roop, and Scott Jorgensen denied Jeff Curran his first UFC victory by taking a unanimous decision.
But regardless if they won or loss, how did each fighter perform? It's time once again to hand out grades to all the main card fighters.