BJ Penn is by no means a waste of talent. He's called "The Prodigy" for a reason. I think any long-time MMA fan would know that. But he does lack a certain amount of drive and/or conditioning it takes to win fights in the UFC. Almost every fighter will admit, conditioning is everything in the sport, and BJ simply doesn't have that.
He's got devastating strikes, but rarely lands anything good. Come to think of it, the last good punch I saw him land, was the one that beat Hughes. But as mentioned, he has little conditioning, and that's what loses fights for him.
I don't see how people can say he beat GSP. Penn won the first round. But GSP clearly won the second and third. If you see it otherwise, you need to stop being biased and giving your boy double points for every shot he lands. St. Pierre landed some better shots, had more takedowns, and was on top of Penn for the most part. What did BJ do besides break his nose in the first?
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