The first half of Saturday's stage to Plateau de Beille has seen three highly tipped riders abandonThe wet conditions and crashes during the Tour's first week and unrelenting pace throughout is beginning to take its toll on some Lance Armstrong's potential rivals. After many of them struggled at La Mongie yesterday, the early part of Saturday's stage to Plateau de Beille saw first Haimar Zubeldia and then Denis Menchov abandon the race with knee trouble. Menchov's loss is particularly hard on his Illes Balears team because he finished seventh at La Mongie and his partnership with Paco Mancebo was looking one of the few threats to Armstrong. More surprising still was the abandon of last year's fourth-placed rider Tyler Hamilton just after the first feed zone at the foot of the descent from the Portet d'Aspet. The Phonak team leader, who lost three and a half minutes yesterday, stopped in the feed zone, then continued for a few kilometres before climbing off at the 84km mark. Phonak team manager Jacques Michaud told French television that the American was suffering with severe back pain as the result of a crash during the first week. Hamilton told procycling a couple of days ago that the injury was preventing him standing on the pedals. More news on this later.