Ngannou’s success against Fury largely came from the fact that Fury was nearing 280 pounds of blubber rather than his more mobile and fit physique from the first Usyk fight for example. Ali’s career heaviest prior to Berbick was against Young, the fight where many believe Ali began losing his mojo. Could Francis replicate his success against Fury here or against any version of Ali?
Doubt. James was already an elite fighter even if he didn't show enough grit and courage in that fight.
I think Ngannou would give a very good account of himself. If Ali doesn't take him seriously (and he really wasn't taking all that many challengers seriously around this time), then I think Ngannou would have a solid amount of success bullying Ali in the clinch because he is the much bigger man and has a far more advanced understanding of grappling. Ngannou also showed against Fury that he's quite good at countering the jab and catching opponents on the way in. His long guard was pretty decent and I liked the way he was jabbing with Fury at points. It should also be remembered that Ngannou is an enormous puncher. I don't really think it's that outlandish to think that Ali would have a tough time with Ngannou and would have some tricky moments. I think he'd probably find a way to win, but it would be a fascinating fight to watch.
Ngannou sparred with good boxers regularly and he was boxing before he did MMA. Carlos Takam had warned people that Ngannou was a world class heavyweight before the Fury fight. Any athlete 6-4, 265, with boxing and ring combat experience, as strong and hard hitting as Ngannou is a legit threat to any boxer.
Honestly Schmeling vs. Ngannou interests me, Ngannou is a sucker for the right hand and Baer said that Max hit harder with one punch than Louis did. On the other hand, it didn’t seem like he could put a dent in Baer, and Francis getting chopped down by AJ isnt that much of a blight on his chin considering the leather he took from 265 pound heavys with 4 ounce gloves. Max’s 190 pound frame could only handle so much of Ngannou’s punches.