I don’t think anyone from that era tops Hagler unless it’s on cuts (to which he was vulnerable from time to time), but if I had to pick my first choice would be Ray Robinson and my other (longshot) possibility would be Marcel Cerdan on the slim hunch that maybe he keeps Marvin off-balance just enough to sneak out a 15-round win.
I think plenty of them give him a fight and of course some of the TOP Men could beat him as well as Hagler might beast them too. TOP Fit, Great Boxers and Fighters a plenty can & will have their wins & losses with each other... living colour is not an automatic default win. in fact, I'd favour long fought out times multiple fights proven fighters over 15 & 20-year careers at the TOP first, but they're not necessarily a given either. Its Boxing at the TOP, there are plenty of greats basically equal with one another.
How about 1938? This content is protected Not sure I'd favour Steele over Hagler, but he did a lot of things well. Great free-floating style. Good bob and weave, light feet, sledgehammer power and an excellent record which speaks well to me of his consistency. He's clearly a guy that put in the hours and had a fire to win. I'd say he's got as good a chance as any from those days and better than most.
It's Burley. Serpentine. That doesn't suit Hagler. Physically his equal, including reach and probably including something close to his chin - no knockout is possible in this fight. Even more economical, probably - has literally all the punches. He's going to slow Hagler down, but he doesn't need to paticake to do it like Leonard. I'd actually pick Burley at his absolute best to get out of there with a weird decision.
Burley is a good pick. Another good pick is a middleweight Ezzard Charles. He was good enough to handle Burley, so he may be good enough to handle Hagler at middleweight.
Burley is a good pick but not the only pick. I think that there are three types of guys that would give hagler problems and his career bears this out. The first would be guys that fight out of a bladed stance and use their shoulders well. Like Burley or how I am pretty sure Holman Williams fought. I say that because Hagler was a very right hand dependent fighter, even as a southpaw. He would have to constantly move to his left to use his right jab and his hook would always be behind their left shoulder. The second would be guys that pressured him intelligently but constantly. He struggled with Antuofermo and there were guys better than him. Third, guys that would make him think because he slacked of fighting while he thought. Duran hit him with right hands early and it took forever for Marvin to get going in what could have been an easy night for him if he had just fought the fight. Hagler was a very good fighter and was always a professional. But he was very beatable, even if it wasn't easy to do.
Robinson beats him on points. Hagler was great to watch, however this might be controversial, but I believe his resume is made to look better than it is. Duran is an ATG, but he was fighting a man 25lbs bigger than him naturally, and Duran weighed several lbs under 160lbs. Hearns was a good 160lbs, but wasn’t elite at that weight, he certainly was vulnerable. Then John Mugabi, who was naturally 154lbs, but he’s known primarily for ‘giving Hagler a good fight’, even when he dropped down in weight after that, he was losing to non-elite guys. I’m not using this to say Hagler was bad, simply to say he wasn’t as proven even at 160lbs as Robinson was.