Could Shavers KO Anthony Joshua before getting stopped himself?

This. AJ's chin issues only really cropped up with Ruiz.

There's something dodgy going in in Joshua's headspace.

I'd pick prime AJ over Shavers any day. He's simply massive, more skilled and has a huge punch himself. However it's also true that AJ lately has been flakey.

So if the question is "could" Shavers KO AJ, the answer is yes. Shavers "could" KO just about any heavy that has been around with maybe a handful of exceptions.

But if we are going prime-for-prime, only a fool would put his money on Shavers.