Based on career resume. Losses count. Tim Witherspoon, Pinklon Thomas, Chris Byrd, David Tua, Alexander Povetkin.
Witherspoon had a lot of potential...but he was only really impressive against Holmes imo. Thomas might have had a much better career had he started earlier. If he'd peaked at the time he fought Tyson, it might have been a significantly different fight imo.
In terms of talent: Witherspoon, Thomas, Tua, Povetkin, Byrd In terms of combination of ability and talent: Witherspoon, Thomas, Byrd, Povetkin, Tua
Chris Byrd: #23. Tim Witherspoon: #25 Alexander Povetkin: #30 Pinklon Thomas: #40. David Tua: Unranked. I think Tua would beat Povetkin, but lose to the other four. Povetkin, Thomas and Witherspoon would both Byrd IMO. Witherspoon beats all but Thomas, who goes undefeated.