Former UFC lightweight and welterweight champion B.J. Penn was already somewhat retired when he decided to step back into the octagon one more time against Rory MacDonald at UFC on Fox 5. He hadn't fought since a UFC 137 loss to Nick Diaz, and stated many times that he thought he was done. Now, he's stuck in the same position again after a one-sided loss to the Canadian prospect. Penn was asked by Inside MMA if he was truly done in MMA now, and he was still surprisingly on the fence:

"I am taking some time to figure it out."

After UFC on Fox 5, UFC president Dana White wanted BJ to hang 'em up:

"B.J. is a warrior. Talk about a guy who doesn't give up, doesn't quit, and just keeps coming. I have so much respect for B.J. I always have, even though the good times and bad times. I‘d like to see him retire. He's got plenty of money, he's got a great family that loves him, he's got babies, a beautiful wife ... He has nothing left to prove to anybody, and everybody loves him. You heard the arena here tonight. I'd like to see B.J. retire."

It's tough to say what Penn will do. He clearly isn't suited to the welterweight division any more. If he's willing to invest the time and effort to get back to lightweight, he could possibly still be a dominant force there. But retirement is the most likely option, and probably the one he should take. Dana's right - he doesn't have anything left to prove.