I think Foster have a good chance at stopping Quarry (through cuts). He could keep him at the outside with his jab and do damage with his right. When Quarry gets to the inside it might be game over at any moment, though. But he definitely wouldn't steamroll Foster like Frazier did. I don't see this going later than the middle rounds. If Foster doesn't cut Quarry early I think Jerry eventually takes him out.
I think Quarry would have been too strong for the light heavyweight Foster. Quarry beats Foster down within eight rounds. It would be entertaining while it lasted though, given Foster's height, powerful left hook and Quarry's tendency to cut. But overall Quarry had far more durability than Foster did, and Quarry's punches could do more damage to Foster than vice verce.
Quarry was harder to KO, but he was easier to cut. So I wouldn't say that he was that much harder to stop than Foster. Foster managed to cut Ali with his jab, so he might well cut Quarry much worse.
Speaking of light heavyweights... What about the fact that Floyd Patteron, WAY past his prime, went 22 rounds with Quarry and was never stopped?
A bleeding Jerry Quarry would have caught Foster, ala Marciano-Charles 2 and would have ko'd him in spectacular fashion in an emotionally charged, revenge motivated fight. Bob Foster, whom I consider one of the greatest lightheavyweight champions, and one of the, if not THE greatest one punch killers of all time, wouldn't be able to knock down Jerry with a baseball bat, or to contain him from avenging his brother's near decapitaion. It would have gone maybe 3 rounds, and would have been supercharged with action. It would have resembled the 3rd round of Hagler-Hearns.
Quarry, at that time, had a different style, more retreating and counterpunching, and that all changed when he fought Joe Frazier in 1969 and when he (Quarry) matured physically.
I see this fight going down much the same way... a motivated Jerry Quarry was a formidable opponent and he would have been hell bent on avenging his brother Mike`s vicious KO loss to Foster. Jerry steamrolls the lanky Foster within 3-4 rounds at most, probably knocking him out for the full ten count.
Patterson had an excellent defense and he managed to dodge most of Jerry's power shots. When he was hurt, Patterson was adept at dancing away from Quarry. Even so, at times Floyd appeared to be close to being stopped in the second fight. Keep in mind also that Patterson landed many punches of his own in these fights. That caused Quarry to play it safe.
Quarry by ko.Foster ,great as he was ,never beat a top 10 heavyweight,Bob has a slim chance of stopping Quarry by tko ,on cuts ,but Jerry should be able to walk him down and stop him.