Angel “El Diablo” Manfredy marched to the boxing ring in Miami on Dec. 19, 1998, to battle an unbeaten lightweight named Floyd Mayweather. Joining Manfredy was another young star: rap-rock artist Kid Rock. He introduced Manfredy to the crowd in the typical “make some noise” fashion. At the entourage’s rear was a third up-and-comer. He donned a black suit and metal-framed glasses. He is decidedly not a boxer nor a trainer nor a corner man nor a pop star. He is Jeffrey H. Brown …