.. What would have changed for Sugar Ray, and indeed the middleweight division as an whole? For example, Robinson was a 5 times champion at Middle weight, is that out of the window? The other guys and champs of the era, are they out of the championship picture? Thoughts?
Assuming Hagler is in title contention from the very beginning of the decade as per the 80s, he'd be almost even money with the Robinson from 1950-52 and assuming Robinson quits for two and a half years like he did in the 50s, then Hagler picks up the vacant title (assuming he hadn't already beaten Robinson) and beats the remaining available contenders - he would be too good for Bobo Olsen, Fullmer and Basilio and he wouldn't drop the title like Robinson did. But by late 1955 he'd be facing Robinson again. I'd favour Hagler at this point but if they met several times (as would likely have happened in the 50s), Robinson might take a decision in one of them.
I think Hagler would have spanked Robinson. Technically superlative with a wide range of techniques and the ability to give as good as he got. I get that Robinson was p4p but Hagler is just tougher and more implacable imho.
To put a downer on things, who is going to touch Hagler? If I am a big name Middleweight I am not fighting the awkward southpaw without a real decent payday. And if no one knows Hagler, I do not think that payday would be there. I can see Hagler be avoided like the plague and eventually giving up before developing into the world class operator we knew.