Yeah. That just happened.
BJ Penn was widely considered a top welterweight even though in his last fight he ended up with a draw against Jon Fitch and was pummeled in the third round by Fitch.
But Penn is a legend and gives Diaz a credible name victory after his last ten fights were against fighters either out of their prime or that were no good to begin with.
Diaz did it in dominating fashion too.
After the first round Diaz destroyed Penn standing in ways no one has ever seen. Eventually in the mid-second round, Diaz made Penn gas after a flurry of body shots that weakened Penn to the point of no return.
Then in the third Diaz continued and even though he didn't finish Penn, he came super close.
Diaz even left his mark on Penn giving him a huge swollen shut left eye and then seems like he made Penn retire.
But this is a big deal for a fighter who previously had no one of name and had not beaten anyone relevant. Then to do it in impressive form is another thing. Sure, Diaz can take a punch, but if he worked on defending his shots better and evolved his street boxing into actual boxing, he could be a threat to UFC welterweight champion Georges St-Pierre.
GSP is sidelined though and his fight against Condit won't be until early next year, so his aspirations of a title fight with GSP will have to wait.