Referred to as the 'Little Troll' by Lance Armstrong, Walsh along with fellow Irishman and "Sunday Times" journalist Paul Kimmage, led the way in exposing the systematic doping rife within cycling, in particular the US Postal Team and its leader, Lance Armstrong. Walsh revealed in the "Sunday Times" in 2001 after a two-year investigation that Armstrong was working with the controversial Italian doctor Michele Ferrari. Under the headline "Champ or Cheat?" "The Sunday Times" asked in 2001 why a clean rider would work with a dirty doctor.