Timestamped video below. I recommend setting the speed to 0.25 to fully appreciate that jab. This content is protected Incredible long range weapon.
Brooklyn 1550 was a great poster who used to come here who died quite young. He sparred with Hagler (had some cracking pics of and Marevelous) and said the jab was awful, as in really good. Inescapable. He said the difference between sparirng Hagler and the other guys from the gym (no names) was that Marvin never wasted anything.
I love the range he gets on his jab, plus how accurate it is, and he much he commits/puts into it. The Sibson sequence I posted above is just an absolute killer, relentless, merciless use of the jab.
One of the best jabs in history. Variably used to unsettle, agitate and hurt; spearing through opponents' defenses, leaving them confused and deterred. Hagler made things happen with that jab. His movement and punch selections off the jab are a sight to behold.
Prime Hagler is surprisingly close to GOAT status. He could beat Robinson, Ketchel and Monzon there, at middleweight. Such an utter destroyer of big, strong talented fighters.