How's Marvin do against the likes of Saul Alvarez? Terence Crawford ? Dmitry Bivol? Gennady Golovkin? Do any of these seem particularly hard fights for Hagler? Anyone you believe he'd defeat with no bother?
Bivol probably beats him by staying discliplined and keeping away. I doubt Canelo would even take prime Hagler on. In any case, Hagler is too tough, too aggressive, and Canelo never had the work rate to beat Hagler or the slickness to out box him. Marvin wins a decision, maybe loses 3 rounds max in a 12 rounder but wins. Crawford has no chance. Crawford has one win north of 154 and that was vs a faded Canelo. If Crawford fights a very disciplined fight and keeps his distance, he could frustrate Hagler but ultimately would lose a decison. GGG was great but too cautious vs quality opponents. For example, when he had Canelo up against the ropes and hurt, he didn't go in for the kill. Hagler was quicker than GGG and Hagler's speed would force GGG into a more defensive role. I think Hagler would outwork GGG in a competitive fight but GGG's power and skill should win him 3-5 rounds in a 12 rounder.
Bivol is, however, two categories different from Hagler. Hagler has never boxed outside MW as far as I can remember. If he gained weight for LHW he would lose. A If Bivol were to lose weight for MW, he would lose easily, if he managed to reach the weight for MW in general.
Hagler would brutalize Alverez and Crawford, they simply didn't have the firepower or skills to keep Hagler at bey and both would get stopped in 8-9 rds max. Bivol and Golovkin were bigger men, however they didn't have the skill set to trouble Hagler. Hagler wins a UD against both men without much of an issue.
Bivol might be too big, Hagler wouldn’t even be a middleweight now. Based on skill he beats them all. I would say Hagler himself was also cautious against better opposition
