10 MMA Fighters Who Never Reached Their Full Potential

10. BJ Penn

"The Prodigy", perhaps comes as a surprise to some to see on this list, due to the fact he is arguably the greatest lightweight to have ever graced the Octagon. He achieved a lot more than most fighters did, but did he "reach his full potential", no.

People started calling him “The Prodigy” because of his fast rise to BJJ Stardom, winning the World BJJ Championships with 3 years and a few months of training. He really is one of the greatest fighters of all time, world class Jiu Jitsu, fantastic boxing - Freddie Roach once claimed Penn was the best striker in MMA. 

Penn held both the Lightweight and Welterweight titles in his UFC career, beating the UFC Hall of Famer Matt Hughes to take the Weltweight belt. Penn is fearless when it comes to fighting, even fighting former UFC Light Heavyweight champion Lyoto Machida at 205 pounds (50 pounds heavier than normal), losing a decision. However his disregard for fighting at his natural weight class is arguably the downfall on his career. 

Often barely training for fights, ballooning up in weight between fights, leading to him taking fights at Welterweight against opponents lesser in skill but far superior in size. This ended in some one sided beatdowns.

It leaves the question, just how great could Penn have been with the right dedication and training?