UFC 137 Results: BJ Penn Retires Following Loss to Nick Diaz

On Saturday night, Nick Diaz made his return to the UFC and faced off against BJ Penn in the main event of UFC 137.

Penn came into the fight off a draw with Jon Fitch at UFC 127, looking to get himself back in the win column and possibly able to earn a third shot at welterweight champ Georges St-Pierre.

After a unanimous decision loss to Diaz, though, Penn dropped a bombshell in his post-fight interview with Joe Rogan.

He announced his retirement.

He said something to the effect of "I can't keep getting beat up like this" and was visibly upset about the loss. Not only was he visibly upset, but he was visibly beat up, as his left eye was very badly damaged—along with the rest of his face.

Post-fight retirements shouldn't always be totally believed, but in this case, it sure seemed like Penn meant what he said.

Diaz was making his return to the UFC, and he came in on a 10-fight winning streak—which included him claiming the Strikeforce welterweight title and defending it three times.

More on Penn's supposed retirement, including direct quotes and info from the post-fight press conference, as it happens.

In the meantime, stay tuned to Bleacher Report MMA for all your UFC 137 post-event needs.

Tim McTiernan is a Featured Columnist for Bleacher Report. For the latest news on everything MMA, follow him on twitter @tmt2393.