Former world title challenger turned trainer Ronnie Shields once revealed the greatest fighter that he has ever worked with. Based out of Stafford in Texas, Shields has coached fighters such as Evander Holyfield, Mike Tyson, though briefly, and Pernell Whitaker to name just a few. “That’s a toss-up between Evander Holyfield and Pernell Whitaker. Talent-wise you just can’t beat Pernell Whitaker. He went up to cruiserweight and he ruled that division without a doubt and then he went up to heavyweight and ruled.