The 195km journey from Lannemezan to Plateau de Beille began with a Category 2 ascent of the Col de Portet-d’Aspet, and two Category 1 ascents of the Col de la Core and the Port de Lers. A 22-man breakaway dominated the early part of the day before the group whittled down and was eventually overtaken by stage winner Joaquim Rodriguez (Katashua) in a determined display of strength up the 15.8km-long final ascent.
But all eyes were on the battle for the yellow jersey further down the road as the race favourites joined forces to repeatedly attack overall leader Froome.
Two moves by Valverde with seven kilometres remaining anticipated the first big attack by Quintana in this year's Grande Boucle. Together, the Movistar duo was able to derail Australian Richie Porte from the leading Sky train and force team-mate Geraint Thomas to falter after almost half a dozen attacks initiated by Movistar.
As Thomas lost ground, the man in the yellow jersey himself had to follow subsequent attacks and, in doing so, demonstrated why he has such a commanding lead of the three-week race.
While the group of GC favourites shed some of Froome’s support team, it was never able to drop the leader himself. Eventually, Valverde led the group home in ninth spot, 6min 46sec behind winner, Rodriguez. Quintana finished in 11th, one second behind his team-mate and on the same time as Froome, Alberto Contatdor (Tinkoff-Saxo), 2014 champion Vincenzo Nibali (Astana) and Tejay van Garderen (BMC).
Valverde maintained his fourth place overall while Quintana held onto third, 3min 9sec behind Froome on the general classification. The Colombian climber still leads the young riders' competition. Meanwhile, Movistar's Gorka Izagirre finished further up the road taking fourth for the day.
The strong ride by the Movistar team as a whole caused it to jump into the lead of the Tour's teams' classification, with more than five minutes on Sky.
"It was a good work from everyone in the team. A difficult day, with really demanding climbs and, above all, serious temperature changes and rain in the finale.
“It took even more energy from us, but we stood it and attacked the leader several times. Sky managed to control all of them - as well as ours, the ones from Alberto, Vincenzo. They dominated the situation pretty well and have shown to be strong, as well Froome and his team-mates.” - Nairo Quintana
While they didn’t get the gap they were hoping for, Valverde and Quintana did demonstrate they are up for the fight for yellow all the way to Paris.
“We'll keep dreaming and trying; there's still a long way to go and everything won't be decided until the final mountain stage,” said Quintana, who expects to have similar form for the remaining mountain stages.
The riders now face four stages and a rest day before taking on the climbs in the Alps.
Stage 13 will finish in Rodez after 199km. The route features several small climbs in its latter kilometres, most notably the non-rated La Primaube, which comes just 10km from the finish line. The Côte de Saint-Pierre, a 570m vertical ascent with an average gradient of 9.6 per cent, will close the day ensuring another exciting test for overall honours.