Hagler actually had great hand speed. And, unlike guys like Mayweather, he was landing hurtful punches at that speed.
It's odd how some heavyweights like Ali, Patterson or Tyson development reputations for their handspeed whilst others like Joe Louis or Joe Frazier don't. The literal first thing I noticed about Frazier was how insanely fast his hands were, and how people fawning over his grit n' heart n' gumption n' determination were actually doing him a disservice lol. Made him sound like the little engine that could and not an ungodly combination of crack-head head movement, handspeed and stamina
Roberto Durán was not quite there but he kept up with Leonard in all terms of speed, him surpassing him in footspeed was a major key in his victory and subsequent educational whooping he delivered on the young Olympian.
Julian Jackson actually had underrated hand speed. His knockouts wasn’t just power and accuracy but also the speed that came with it as well. Mike McCallum himself claimed that Julian Jackson had the fastest hands out of all the fighters he faced, even over Roy Jones Jr. Best I Faced: Fastest hands: Jackson -- He was quick, man. Thats why he got so many knockouts. Everyone focused on his power and then he’d get you with a punch you didn’t see. They landed on you -- boom! -- from out of nowhere. Kalambay and Toney were also fast. So was Jones, obviously, but I fought him when I was older and had slowed down a bit.
For many years Joe Louis was noted for his hand speed. I had a book on the heavyweight champions written right after Liston won the title- he was included as an appendix to the original text- and they referred to Floyd Patterson as the fastest heavyweight champion since Joe Louis. A lot of guys that hit hard get overlooked for their speed because many have an absurd idea that hitting hard and hitting fast are mutually exclusive. That only happens if you haven't been taught right.