SRR, Jones and Hopkins. A match with Monzon would be anyone's. There's a handful of others that could give him a very good fight too. The riddle of a Burley, for instance, might put him off his game a little.
Hopkins would be a frustrating fight if anything, with Hagler for me. Marvin would get the win thru sheer ruggedness and strength. But Bernard will take him to a close decision. Jones, I don't normally pick against but I like Marvin to take a, another, close decision win. Not much between em for definite. I see Hagler having to race and catch up with Jones and having decent judges to. Lol. Burley s an interesting one to throw up John. Monzon, tough fight again. Dare I say Hagler may need to fight him at home to get the decision??
I think all of those fights might sit on a razors edge. I take Hopkins to be too savvy and adaptable.
I honestly think Giardello could pull off one in a series of three. An awkward style for Marvin to deal with.
Possibly Michael Nunn. If he can stay focused for the entire fight, has the reflexes, reach, hand and foot speed to win a decision.
Only a handful could beat Hagler, at his very best. But, I'd not bet on any of them. Monzon is the most likley to succeed, in my opinion.
Monzon and Robinson; I think Hagler was the more consistent, perhaps even better middleweight, but Robinson's style plays hell with him. Greb too, while we're at it. He's Vito Antuofermo but in capital letters.
Greb, Mike Gibbons, Sam Langford, Robinson, Stanley Ketchel, Mickey Walker, Les Darcy, Holman Williams, Charley Burley, Billy Papke etc.
Freddie Steele would win the first match. Criminally underrated. He would have the size and experience ( 125 wins - only 5 losses )
Very few, however one thing to note as Sun Tzu says the man who divides his force everywhere is weak everywhere. Hagler was very all round good however this is in someways can be an issue if a fighter can force you into there fight you will lose on experience. Doing that would be a tall order with Marvin but a few durable technicians could pull it off a Griffith or a D1ck Tiger could have the tools.
Monzon, Greb , and Robinson would get 1 but I like Hagler to take two out of three. I'd favor Hagler over Monzon by the way.