Last night, I rewatched a recording I have of Ali-Bugner #1--it's the entire 12 rounds, not the 9 of 12 widely available.
In watching closely, it was clear that Ali was stalking Bugner the entire 12 rounds, except for maybe 30 seconds total when he chose to dance and circle. But basically, he was walking down Bugner all 12 rounds. Bugner was the one circling, nearly always defensively.
What struck me for the first time was how perfectly Ali cut the ring off on Bugner all night, every second. No matter how many steps Joe took to his left, Ali was instantly RIGHT in his face, able to throw punches that landed. Ali didn't "follow" Bugner as so many fighters do; in the most subtle and natural way, he simply leveraged skills honed over many years to cut the ring off on Bugner at every step. The more I paid attention to it, the more impressive it was.
I've never seen this skill evidenced better by any fighter, yet Ali is never noted for it. Maybe because he had so many other fine abilities. Ray Leonard showed it against Hearns #1 most notably, but to me probably not quite as well; he did do some "following" that cost him extra paces . . . but maybe because Tommy was better and faster than a Joe Bugner. Wilfredo Gomez was probably the other boxer in modern times with this skill at such a high level that comes to mind, given his outstanding footwork generally.
Wondering if anyone would care to weigh in on this admittedly very micro topic with other examples of excellence in this skill.