Chris Froome and Bradley Wiggins are second and third respectively in the overall standings after Juan José Cobo (Geox) climbed to victory on an epic stage 15 of the Vuelta a Espana to take the leader's red jersey.
Cobo made his move with just under seven kilometres remaining on the fearsome final climb of the Alto de L'Angliru.
That 12.5km ascent had an average gradient of over 10%, with ramps of up to 23.5% in places, and not surprisingly it splintered the field - with even two televsion motorbikes struggling to cope with the extreme steepness of the slopes.
With 5km to go, Cobo was 13 seconds ahead of a select group that contained both the red jersey of Wiggins and Froome - and the Spaniard extended that advantage to 40 seconds going under the 3km banner.
Cobo had started the day just 55 seconds adrift of Wiggins in fourth on the general classification and he was able to maintain his momentum all the way to the line for both the stage victory - plus a 20 seconds time bonus - and top spot on the overall standings.
He finished 48 seconds ahead of Wout Poels (Vacansoleil), Denis Menchov (Geox) and Froome, with that trio a further 33 seconds in front of fifth-placed Wiggins and Igor Anton (Euskaltel-Euskadi) in sixth.
It all means that going into the second rest day Cobo leads the GC by 20 seconds from Froome, with Wiggins 46 seconds back in third and Bauke Mollema (Rabobank) 1:36 adrift in fourth.
Afterwards Team Sky Sports Director Steven de Jongh was proud of the efforts of his riders, while also paying tribute to the day's winner as he said: "You can see that our guys took time from nearly all the other GC contenders which was a great effort but unfortunately Cobo was just a bit too strong and put in a lot of time to both Brad and Chris; fair play to him for that.
"We're still second and third overall and the boys did an amazing job. We can be really proud of their performances because that final climb was incredibly steep - even the cars were struggling with it."
Looking to the final week of the race, de Jongh added: "We'll take it day by day now as we have been doing and maybe opportunities will arise which we'll do our best to take. Second and third on the GC is also something significant to defend so it's going to be an exciting last week.
"Before then the riders will all look to get some well-deserved rest tomorrow - they've done a fantastic job controlling things over the last week."
The 142.2km stage from Aviles had earlier featured a three-man breakaway comprising Dimitri Champion (AG2R), Simon Geschke (Skil-Shimano) and Andrew Talansky (Garmin-Cervelo).
They escaped after 37km and quickly built up a maximum advantage of exactly six minutes but it was only a matter of time before they were caught and that happened on the early slopes of the day's penultimate climb up to Alto del Cordal.
Then it was all about the feared final Angliru climb and Carlos Sastre was the first to attack as he forced the pace for his team leader Cobo.
Carlos Barredo (Rabobank) and Anton both made their own moves in the first half of the ascent but it was Cobo's surge as the gradient hit over 13% with 7km remaining which ultimately proved decisive, though Froome and Wiggins once again produced magnificent performances of their own.
Cobo now has six stages to defend his lead before the finish in Madrid next Sunday.
Lots more on the race at the Sky Procycling website