he once said his defense was in his legs but really, it was a lot more than that. He just had the gift. You can see him turn his chin just enough to avoid shots, you can see a guy, fast guy, like floyd patterson throw a punch and ali parries it perfectly. Ali said he didn't really know how he did it himself, that he would just a big glove passing his face. So, his style might have been based on movement and distance but it was also a lot more than that. Many of his championship 60's fights, when he was at his best, show him rarely taking a good punch. Those were good fighters though, there were times he was gotten to and if you watch, he would look dazed. Chuvalo caught him with some great punches, even poor cleveland williams had him hurt once which some think is the real reason he fought so hard to take him out so fast.
It's not really enough to just be fast and to move away from one punch, the hard part is not moving into other punches and dodging combinations. So, if you move left or right away from a jab, you have to be ready to evade a right or a hook. Then we can talk about absorbing a punch once it lands by riding with the force, taking out most of the energy, ali could do all of those things. As we all know, in the seventies he lost his legs, didn't dance as much and his reflexes were not the same, on top of that, he foolishly thought that his toughness came from taking punches from sparring partners before fights, he believed you could condition your chin like you condition a lot of other things. And then he got lazy and uninspired in fights.