He was knocked down also by Steve Pannell (first time in his career), another concussive puncher.
I don't think his chin is anywhere near as bad as its made out.
The guys who have hurt him, dropped/stopped him have all been very heavy handed. Sanders hit like a mule! Brewster & Peter could sure crack
I'd say most was more from fatigue than him having a bad chin.
The first knockdown in the Peter fight wasn't an illegal punch & the second was a push.
I really don't think his chins even bad & it certainly is not as bad as its made out to be.