Frazier through sheer work rate. Though it will be competitive. Witherspoon had a good right hand and that might stun Frazier. Of course, as the old saying goes, never hook with a hooker. I am afraid Tim will hook with Frazier but i can't see him winning that. Witherspoon isn't a dancer type who will try to keep Frazier at bay with his feet. He does have a strong jab, good defense and good power. I see Witherpoon winning the first few rounds, landing some hard shots, perhaps even hurting Frazier. But Frazier will keep coming forward and start taking over with body work and hooks. Frazier will find gaps in the cross guard and start upping the pace. Good as Witherspoon was, he wasn't a high output fighter like Ali. And while he could punch, he was never a Foreman or Shavers type puncher. I can't see Witherspoon beating a high output fighter like Frazier though his size, power and skill will be enough to make it a hard fought and competitive fight. Frazier UD 15, something like 9-6. Frazier very close UD 12 if we are looking at 12 rounds, maybe something like 7-5. If they fought 3 times, could Tim maybe edge one? Possibly. But i wouldn't bet on it.
Good analysis.At his best Witherspoon was a helluva fighter,and he was definitely a very serious puncher. However to beat the prime Joe Frazier a fighter really did have to have absolute nuclear punching power as possessed by elite punchers like George Foreman or Sonny Liston. Unless,of course,your name was Muhammad Ali.