How bad was Ali's defence?

If you view Ali in the Cat Williams and Folley bouts you see what his defense was geared to do and how it required a physically prime Ali to carry it out. Apart from that as many have said he didn't know the basics in any category, he never learned to catch or parry or slip and its amazing none of his amateur coaches put a end to his pulling his head back. That being said the very prime Ali likely would have beat any of the heavy greats.

 

Foreman actually named Ali as having the best defense of any of his opponents, due to his ability to slip and counter in mid-ring.

 

Ali did slip, to the inside, and he also parried. What he often didn't do was just to have his hands in guard position so he was protected without having to react. His defense was primarily reaction based, and that will come back to haunt a fighter when his reactions slow down.

 

Ali was one of the best defensive fighters of all time, but even later in his career it wasn't too good and he started realying too much on his ability to take a punch and ring generalship

 

Reliance on chin is why he suffered Parkinsons in the end. A very Bowe like ending. He also stopped training properly for fights which you could tell from his physical appearances.

 

Watch Ali vs Ernie Terrell. He was amazing.

 

Ali's defence was dreadful from 1970 onwards.

He was slurring his words badly by 1977, and probably before then.

He took way too many punches.

 

I agree.
He shouldn't have been taking punches from guys like Rudi Lubbers and Chuck Wepner. If he'd got himself in top shape for those types, he would have reduced the amount of punches he took.
He also fooled around in sparring too much too, showing off, taking punches.

 

The Ali who fought Shaves was way past it

In his prime Ali relied on hand and footspeed. He would have boxed circles around Shavers when he was prime.

His reflexes were significantly slowed by the time he faced Shavers.

He had the chin to take Shaver's bombs, otherwise he would have lost that fight.