Eurosport - Mon, 19 Jul 16:21:00 2010
The Saxo Bank rider from Luxembourg saw his chain come off on the final climb of the day, the hors category Port de Bales with a summit 21km from the finish.
That cost the 27-year-old around 30 seconds and he lost further time on the long, rapid descent to the finish, eventually finishing 39 seconds behind the defending champion.
That gives the Spaniard an eight second advantage heading into Tuesday's big showdown into Pau although he was booed on the podium for breaking protocol and attacking a rival after a mechanical problem.
French champion Voeckler was part of a 10-man breakaway that formed midway through the 187.5km stage from Pamiers and he dropped his fellow escapees on the 19.3km climb of the Port de Bales.
The breakaway party formed after 93km and featured Johan van Summeren (Belgium/Garmin), Serguei Ivanov (Russia/Katusha), Alessandro Ballan (Italy/BMC), Francesco Reda (Italy/Quick Step), Lloyd Mondory (France/Ag2r-La Mondiale), Brian Vandborg (Liquigas/Denmark), Luke Roberts (Australia/Milram), Sebastien Turgot (France/Bbox Bouygues Telecom), Aitor Perez Arrieta (Spain/Footon-Servetto-Fuji) and Voeckler, also of Bbox Bouygues Telecom.
After the peloton had thwarted a succession of early escape attempts the 10 men were quickly allowed to open up a large gap as they crossed a pair of category two climbs in quick succession, the Col de Portet-d'Aspet and the Col des Ares.
Their advantage was 11 minutes as they hit the foot of the Port de Bales where Schleck's Saxo Bank team set a rapid pace which whittled down the peloton to an elite group.
Schleck, who had promised to stop playing cat and mouse after Sunday's opening stage in the Pyrenees, had just made his second attack on the ascent to the 1755m summit when he suffered his mechanical problem.
Contador followed his compatriot Sanchez, regarded as one of the best descenders in the business, down the hill as Schleck fought to regain the lost ground.
As Voeckler crossed the line to claim France's fifth stage win of this year's race, the destiny of the maillot jaune was still in question.
Ballan outsprinted Perez for second place, one minute and 20 seconds behind the leader, as Contador, Sanchez and Menchov caught five more members of the original escape to cross the line 2:50 behind Voeckler.
Schleck, whose 31 second lead at the start of the stage already appeared too slim ahead of the final 52km individual time trial to Pauillac which Contador is likely to dominate, came over the line with Jurgen Van Den Broeck and Alexandre Vinokourov 3:29 behind.