If we are talking about Ali post-1979, then Ray Marcer could perfectly be one Trevor Berbick (RIP). However, the Ali who won his second championship in Africa, then it is hard even to put Mercer in BIG George Foreman's position and place... A prime Ali simply clowns with such an individual, actuallly like Wlad Klitschko did with an aging Mercer.
No version of Ali stops the granite-chinned Mercer, unless we're talking about the ancient Mercer. Ali by wide decision. Mercer probably beats the 1978 Ali, which isn't saying much. Ali was badly declined and slurring his words by then.
Everyone knows prime Ali destroys Mercer, but people seem to thing for some reason am talking about that Ali, 78 Ali vs 95 Mercer is closer than people are making out