If Duran was born over 160 he would have kicked Hagler's ass on the inside. He would have been a 160 nightmare, especially for Hagler.
Wrong. Hagler did not have the offensive style -even in his prime, to stop an inspired early 30s or younger Duran. For all intents and purposes, one man on his record had the tools to render Duran physically incapable of finishing a bout -and that man is Hearns. Hearns is about as different a puncher from Hagler as you can get. Duran could read Hagler's shots and could do what was necessary to evade them or roll with them. Hagler's shots were heavy and Duran was too defensively skilled to get stopped by those. I wouldn't completely rule out a stoppage due to exhaustion, but find it unlikely. Duran's fire could burn for 15 rounds easily. Duran had over a 100 fights and he had his share of trench wars -in fact, he invited these. How often did you see him the worse for wear after 15 rounds? He knew how to avoid getting nailed and his chin was exceptional.
Hagler was a good puncher, but its arguable that he packed the same kind of punch Hearns did at the weight. Their styles were different. Hagler seldom came out the traps smoking the way Hearns did. No way does Hagler stop Duran if he fought more aggressive. He got to a tired Duran during rounds 13/14/15 and still couldn't stop him. Not sure a fresher Duran, physically and mentally, gets taken apart.
Hagler was a little disappointing v Duran but at the end of the day he won. Duran was an all time tough guy regardless of weight. A lot of figters underestimating Duran and ended up with their butts kicked. Being champ is about winning nothing else. Hagler's tactics worked, if Hagler was wimping out and backing off Duran, you can be sure Duran would have went straight at him and forced the pace. That didn't happen, the fight stunk because Hagler took away Duran's offence.