Certainly leonard and hearns could have... Robinsons era was far different then Haglers, and so were his opponents
In terms of styles, I'd say Vito gives Robinson the most trouble of all the guys Hagler fought. I think he's similar to Fullmer in the regards of his crazy workrate, great chin and how he fights really close.
I think Hearns with the jab.. If he tried to land the right off of it and the left hand off the side.
Hearns probably would give Robinson the most problems of Haglers opponents. His height, reach, speed, power and boxing skills would certainly be a challenge to overcome by any fighter in history. Of Robinsons opponents I'll go with Randy Turpin if I had to pick just one. Turpin was one of those guys that seemed to do everything well. He could fight on his toes, counter, could hit hard, and was awkward, unpredictable. Also he was a natural middleweight, the weight fit him like a glove. He could be the type to make Hagler "Overthink" what's in front of him, by the time he figures out what he should do, the fight would be practically over, Turpins wins the dec. In a rematch though, I see Hagler destroying Turpin much easier than Robinson did in their rematch.
Tommy does have the height but is not Robinson something like 5 -11 at least? and Does Robinson not have speed of his own? This will be a competitive match Turpin isnt beating Hagler. I dont even see this being that much of a challenge to Marvin. too straight up and stiff, like Minter but without having the problem with cuts, and better power. Even so, Hagler has most of the edges, except for height, and gradually breaks him down in typical fashion, first with the jab, adding hooks to the body, taking very little in return, intensifying his attack while closing the distance, further beating him upside the head and wearing him down Fully Obel style
Classic for sure, can you see Robinson perhaps actually doing more damage to himself by fighting Duran's fight? Duran could be an absolute devil here, he'd have to be of course meeting Sugar at his best weight.