While Penn struggled with conditioning, St. Pierre’s issues were in his head. He sometimes questioned himself despite overwhelming evidence of his own success. He once lost to Matt Hughes, then admitted the nerves over facing a legend were the culprit of his underwhelming performance. The problems reached their nadir when St. Pierre was KO’d by major underdog Matt Serra in his first title defense. Like Penn, St. Pierre used the losses as motivation, utilizing a sports psychologist to overcome his issues. The results have been jaw-dropping. In his last four fights, St. Pierre his steamrolled his opposition, winning back the welterweight title and defeating three other top five 170-pounders in Josh Koscheck, Matt Hughes and Jon Fitch.

For fans, the best part about this matchup is that these two have almost no holes in their respective games. You could run down a list of skills, and it’d be difficult to give one a significant edge over the other in any single category. The biggest edges are St. Pierre’s wrestling and Penn’s jiu-jitsu, but neither advantage is substantial. Look at the other champions, and you can point out flaws: Brock Lesnar is still green after only four pro fights, Rashad Evans has never exhibited a submission game, and Anderson Silva’s wrestling leaves much to be desired.

But St. Pierre and Penn are complete machines of violence, able to overwhelm their opponents wherever the fight goes and whatever style is employed. Because of that, it is hard to decide a true favorite. As the gambling line goes, St. Pierre has been installed as the favorite, likely because he is a naturally bigger man than Penn, outweighing him by about 15-20 pounds. To Penn, however, size is no issue. He once fought unbeaten light-heavyweight Lyoto Machida to a close decision loss despite giving up 30 pounds.

It is essentially a perfect matchup, champion vs. champion, all-time great vs. all-time great with legacy meaning more to both than any piece of shiny hardware.

I became a combat sports fan in April 1985, watching the legendary Thomas Hearns-Marvin Hagler boxing title fight, which had bell-to-bell action and is regarded as one of the best boxing fights ever despite going less than three rounds.

MMA needs an epic like that, between two prime fighters competing not only for the moment, but for legacy.

With the St. Pierre vs. Penn sequel, that day arrives.