In the old days, guys like Sullivan and Dempsey didn't fight all that much once they became champ because there were easier ways to make good money. Sullivan hired people like Muldoon to get him in shape when he'd been off for a time.
For what it is worth, I don't think that Heredia, who ever he is, had anything to do with Marquez ko'ing Pac. I thought that Marquez would time that right hand in their first fight; I saw it watching him and thought it was inevitable. And it was, it just took one of the two smartest guys fighting today more than 40 rounds to do it. But Pac knew it was coming, too. Look how he bailed out as he threw his left hand. He got the taste of blood, though, and forgot. Brought the left foot up so he could sit down on his hook.