Its would be easy for any foe of Ullrich, Basso or Valv...to nail their doping 'supplier'.
E. Fuentes was an athlete himself and hurdled under the tutelage of Manuel Pascua Pizueras a national Track and Field coach. In the 1980s Pascua convinced him to give up Gyne and start preparing Spanish athletes for the 1984 Olympics (guess they new what the American's were doing and wanted to match them, who knows). Fuentes trained another hurdler named Cristina Peres who tested positive in 1988 Olympics, he later married her.
Fuentes and Pascua where basically kicked out of Spanish Track and Field that year and then as a team Doctor Fuentes hooked-up with ONCE (Siaz), then Kelme (Siaz), then Lib Seguros, the last 2 incognito. He quickly assisted many of those riders to win stages in GTs and the Vuelta for example. He was very good at his job and was in demand. Of note, Pascua's cycling brother worked with Orbea in 1985+. Those Pascuas'! Then He worked with innumerable athletes in Cycling as we all know; Operation P.
Just saying, it would be hard 'not' to know of Fuentes, his abilities and maybe someone 'helped crack the Omerta' by revealing to certain authorities his disposition and taking down a pile of competition, or old rivals, all in one day.
NW