The Spanish national time-trial champion had been in a breakaway group with David de la Fuente for much of the day and when they reached the peak of the Cote de Saint-Jean-de-Donne, Sanchez pushed away from the chasing pack, finishing six seconds ahead of Stefan Schumacher in second.
It is the 24-year-old Caisse d’Epargne rider’s second major stage win of the season, after a similar victory in stage seven of Paris-Nice.
Schumacher, of Gerolsteiner, pipped Kim Kirchen to second place, but the Luxembourger stays in the yellow jersey for another day.
With King of the Mountains leader Sylvain Chavanel struggling at the back of the field, De la Fuente capitalised, leading Sanchez and two other riders over the category two climbs of the Col D’Entremont and the misty summit of the Pas de Peyrol.
De la Fuente, who finished second to Michael Rasmussen in the 2006 climbers’ competition, secured the four points necessary to put into the polka dot jersey when he broke away over the final climb.
The Saunier Duval climber leads Frenchmen Chavanel and Thomas Voeckler by one point, but he was fortunate to escape a nasty accident while descending the Pas de Peyrol, sliding on the wet surface and almost going headlong over a barrier.
Sanchez was evidently delighted when he took the stage win, with hands aloft way in advance of the line.
“From tomorrow, I am going to return to my team role, and help Alejandro (Valverde) and Oscar (Pereiro), the two riders in our team capable of delivering the maillot jaune in Paris.” Kirchen faced no real threat to his yellow jersey on the 159km mid-mountain stage, with 21 other riders all finishing at the same time.
Kirchen, of Team Columbia, leads Tour favourite Cadel Evans by six seconds in the overall standings. The big loser, for the second successive day, was Lampre’s Damiano Cunego, who crashed and was dropped at the foot of the Saint-Jean-de-Donne.
Spanish rider Manuel Beltran has tested positive for the performance-enhancing substance EPO during the Tour de France, according to French sports daily L’Equipe.
The newspaper said on its website that Beltran’s A sample tested positive following the first stage of the Tour last Saturday. Beltran finished the stage 25th. He finished Friday’s stage in 26th place, three minutes 20 seconds behind leader Kim Kirchen. If confirmed, Beltran would be the first rider to fail a doping test during this year’s Tour.
Earlier on Friday, the French anti-doping agency reported that tests conducted prior to the start of the Tour returned no positives tests but a few abnormalities.