The best version of Douglas stops Coetzee in 6-8 rounds. But, if Buster shows up out of shape (as he often did) he likely gets stopped instead.
The Douglas that beat Tyson would dismantle Coetzee inside 8 rounds. The version who melted against Tony Tucker would get rolled right over.
Douglas and Tucker fought at a very high pace, and Douglas looked good for the first 8 or 9 rounds. I don't think Coetzee could do what Tucker did. Because Coetzee always had stamina issues. Douglas outboxed Tucker, he can outbox Coetzee.
Coetzee generally folded like a card table when he met one of the Yank athletes who wasn't on a coke bender. Not sure he possessed the mettle to push Douglas the same way. James KO10