Hasegawa was a bit of a naive reckless dunce, though a very talented one. He got undone a couple of times by basic sneaky punching against guys he should have run over. More recently I'd always thought that Sor Rungvisai had underrated ring IQ, but then he went and fought orthodox against Estrada in the rematch and handed him the fight on a platter.
Also, he reached a point where he actually started training himself. He only had Garcia to join up on fight week to work the corner. Donaire stopped learning.
I was at both of those fights and that was my feeling. Was surprised at his IQ and skill in fight I then surprised how dumb he fought and how dumb he was to stay on that stance the whole fight.
I'll have to watch the last few rounds of the second fight again, but what made it worse iirc was him eventually switching back and immediately looking like a different fighter and Estrada looking more uncomfortable straight away. Bizarre fight, although credit where it's due to Estrada, he was really good to watch that night.
It was more a particular style issue with Hagler, he had a high IQ in the ring. But he was reluctant to force the issue against certain styles.
I would think that Iran Barkley and Doug DeWitt would be above Benn in the list. After all, they were foolish enough to have a stand up fight with a man who specialised in them. We know how they turned out. I don't think Eubank lacked IQ, I just don't reckon he was very talented. He was immensely strong and tough so he focussed on bringing those attributes to a fight.
That's a bit hard on Howard. I always thought he was rushed in his pro career and came up against some excellent Fighters. To me, lack of power in the pro game was his problem.
I think it was the reverse for Eubank. He was very physically talented. Had fast hands, good reflexes, and big time power.... he just lacked brains.
Do you have a source for Duran being Hagler's idol? I don't believe I've ever come across it but could be wrong.