Chris Froome lost almost three minutes on overall leader Nairo Quintana as Gianluca Brambilla won stage 15 of the Vuelta a Espana.
Movistar's Quintana and Tinkoff's Alberto Contador were among a large group that broke away from the peloton early in the 118.5-kilometre stage, from Sabinanigo to a summit finish on the Aramon Formigal in Sallent de Gallego.
Each had two team-mates in the breakaway while Froome was left to lead the chasing pack with little support from his Team Sky colleagues, aside from David Lopez.
The leading group pulled two minutes clear climbing the Alto de Petralba and kept pushing on the Alto de Cotefablo.
Contador took two intermediate sprint points but it was Quintana who surged away along with Brambilla with 1.5km to go as the Spaniard lost touch on the climb to the summit.
Brambilla won the stage by three seconds but Quintana, crucially, finished two minutes and 37 seconds ahead of Froome to take his overall lead over the second-placed Briton to 3:37.
Esteban Chaves (Orica Bike-Exchange) lies third, a further 20 seconds back, with Contador fourth and Chaves' British team-mate Simon Yates fifth.
"We knew it was a short stage, so at the start of the day everyone wanted to attack," Brambilla said. "We were with the red jersey within the breakaway, so we weren't sure, but I knew that I was in good shape."
"I started to believe in the victory 10 kilometres from the finish. I saw Contador was starting to fade and I had to follow Nairo. I knew that he was looking for time and if I sat in it was general classification for Quintana and the stage for me."
