Veteran American Chris Horner regained the race leader's red jersey at the Vuelta a Espana by climbing to a solo victory on stage 10's summit finish on Alto de Hazallanas.
The 41-year-old RadioShack-Leopard rider surged away from a small group containing all of his rivals for overall victory 4.6km from the finish line and powered on to claim his second stage win of the race.
Vincenzo Nibali (Astana) was the only man to launch a counter and crossed the line 48 seconds down in second place, with Alejandro Valverde (Movistar) leading the other four chasers home in third, 1min 2sec adrift.
The result sees Horner, the oldest man in the race, move back to the top of the general classification and he now takes a 44-second lead over second-placed Nibali into tomorrow's first rest day, with Ireland's Nicolas Roche (Saxo-Tinkoff) 53 seconds down in third.
Moreno falls away
Horner said: "I thought if I could get a little gap that the others would play with some tactics behind me with none of them really wanting to work too hard. I don't expect to hold the jersey after the time trial [on Wednesday] - that isn't my specialty and Nibali is a very good time triallist."
Previous race leader Daniel Moreno (Katusha) was dropped 5.5km out from the finish line and shipped 2min 22sec on the day, while Samuel Sanchez (Euskaltel-Euskadi) and Team Sky pair Sergio Henao and Rigoberto Uran all also sustained heavy losses on a severely difficult stage that gave the overall standings a major shake-up.
Played out in roasting conditions in southern Spain, the day came down to two back-to-back Sierra Nevada climbs in the final 40km.
Horner's team-mate Fabian Cancellara blew the peloton to pieces on the first of them, the category-one Alto de Monachil, before Movistar took over and continued to thin down the front group through a powerful combination of Sylwester Szmyd and Jose Herrada.
Three survivors of the day's breakaway - Tomasz Marczynski (Vacansoleil-DCM), Diego Ulissi (Lampre-Merida) and Georg Preidler (Argos-Shimano) - led on to the final climb of the especial-category Alto de Hazallanas, which includes steeps ramps of over 18 per cent, but soon only Marczynski remained and he was eventually swallowed up just over 5km from home.
The catch acted as a trigger for Horner, who gently rode away from the likes of Nibali, Valverde, Joaquim Rodriguez (Katusha), Ivan Basso (Cannondale) and Roche, and swiftly set about building up a lead of over 30 seconds.
His rivals offered no response until Nibali finally realised the severity of their plight and set off alone in pursuit 2km from home, but by now Horner was 50 seconds up the road and despite chasing valiantly, the Italian could not close the gap.
Earlier in the day, a crash in the neutral zone forced Barry Markus (Vacansoleil-DCM), Alberto Losada (Katusha) and Bart de Clerq (Lotto-Belisol) to abandon the race, while Britain's Andrew Fenn (Omega Pharma - Quick-Step) and Thomas de Gendt (Vacansoleil-DCM) were both disqualified for holding on to team cars.
Stage 10 result
1 Chris Horner (USA) RadioShack-Leopard, 4:30:22
2 Vincenzo Nibali (Ita) Astana, +48
3 Alejandro Valverde (Spa) Movistar, +1:02
4 Ivan Basso (Ita) Cannondale, same time
5 Joaquim Rodriguez (Spa) Katusha, st
6 Thibaut Pinot (Fra) FDJ, st
7 Nicolas Roche (Irl) Saxo-Tinkoff, +1:10
8 Igor Anton (Spa) Euskaletl-Euskadi, +1:25
9 Domenico Pozzovivo (Ita) Ag2r-La Mondiale, +1:25
10 Rafal Majka (Pol) Saxo-Tinkoff, +1:52
12 Daniel Moreno (Spa) Katusha, +2:22
13 Samuel Sanchez (Spa) Euskaltel-Euskadi, st
26 Sergio Henao (Col) Team Sky, +3:58
27 Rigoberto Uran (Col) Team Sky, +4:08
1 Chris Horner (USA) RadioShack-Leopard, 40:29:14
2 Vincenzo Nibali (Ita) Astana, +44secs
3 Nicolas Roche (Irl) Saxo-Tinkoff, +53
4 Alejandro Valvrde (Spa) Movistar, +1:02
5 Joaquim Rodriguez (Spa) Katusha, +1:40
6 Daniel Moreno (Spa) Katusha, +2:04
7 Ivan Basso (Ita) Cannondale, +2:20
8 Thibaut Pinot (Fra) FDJ, +3:11
9 Rafal Majka (Pol) Saxo-Tinkoff, +3:16
10 Domenico Pozzovivo (Ita) Ag2r-La Mondiale, +3:28
15 Rigoberto Uran (Col) Team Sky, +5:12
23 Sergio Henao (Col) Team Sky, +7:08
- Green (points classification): Daniel Moreno (Katusha)
- Blue polka dot (mountains classification): Chris Horner (USA) RadioShack-Leopard