All the skill in the world doesn't matter if you can't finish the fight early or fight into the later rounds. Conditioning isn't just as important as any other asset. Conditioning is the most important asset an athlete can have.
From my personal experience, I know a lot of Div. I and II wrestling all-americans who never pulled ahead in the first period. Started pulling away in the second and blew everybody out in the third. Their greatness wasn't due to overwhelming skill or fancy technique. It was due to solid technique combined with unstopable endurance.
BJ and BJJ fanboys take note.