Spinks out slicks Coetzee to get a points win. But, he'd have to be vigilant against Coetzee s dangerous right hand.
I think Coetzee at his best would stop Spinks. Spinks' HW resume is very skinny for me. Squeaking past the aging & tired Holmes (their 1st fight was the aging Holmes' 3rd defense in 6 months) & stopping a rusty and addicted Cooney is no guide to indicating that Spinks was strong enough to take on full blown world class heavyweights like Coetzee, or peak versions of Thomas, Page, Weaver, Witherspoon, Berbick for that matter. Although Spinks could be awkward and elusive against these guys, I don't think he had the physical strength or enough "pop" on his shots to keep them at bay, keep them honest. All the above had enough inconsistencies that Spinks could beat them on one of their admittedly regular off-nights (Berbick - ST Gordon for example). But at their best, I reckon all the names I've listed above would beat Spinks. I think that Thomas, Page, Weaver would all likely beat Spinks inside the distance.
Coeztzee asks if there are any more brothers to fight as he crushes Mike in 4. Coetzee was a good boxer.
Coetzee by 8th round stoppage. At some point, Gerrie is going to catch Mike, and I don't see it ending well for him. Cooney wasn't truly right and Holmes was old.
Spinks is the better boxer no doubt. The question is whether Gerrie would catch him with the straight right hand. That is a tough one. My money would be probably be on Spinks by decision.