Tejay van Garderen (BMC) took his second career WorldTour victory on the summit of La Molina on stage four of the 2015 Volta a Catalunya, with Team Sky's Richie Porte coming in second ahead of Alberto Contador (Tinkoff-Saxo).
The American slipped out of GC contention on Wednesday's stage three having crashed on a descent, but seemed to use the 15 minute deficit to his advantage as he attacked with only around 3km to go and wasn't immediately pursued by the overall contenders.
Contador was the first of those to respond to Van Garderen's move but was tracked by his BMC teammate Darwin Atapuma.
Vasil Kiryienka (Team Sky) who had already made an earlier move up the category one climb, was able to use his position to help bridge Porte over to Contador, with the Tasmanian then attacking as the road rose up again in the final 500 metres to put five seconds into the Spaniard.
But Porte's move was too late to catch Van Garderen, who crossed three seconds ahead to add the stage win to his other mountain top victory in the same race last year.
Overall leader on the road, Pierre Rolland (Europcar) was unable to hold onto his jersey, getting dropped early on the climb, and slipping out of the top 10 by the time he crossed the line five minutes later.
Porte's attack wasn't enough to quite see him to the top of the GC, as Rolland's stage one breakaway companion, Bart De Clercq (Lotto-Soudal) finished well enough on the stage to maintain a 21 second gap and take the leader's jersey.
Dan Martin (Cannondale-Garmin), who had attacked with around 5km to go, managed to fight his way back to finish level with Contador, and now sits fourth in GC.
Friday's stage five looks less likely to have a major influence on the overall standings, but features a category two climb close to the finish to present yet another difficult finale in this race.
Volta a Catalunya 2015 stage four (188km), Tona - La Molina
1. Tejay van Garderen (USA) BMC, in 5-00-36
2. Richie Porte (Aus) Team Sky, at 3 seconds
3. Alberto Contador (Esp) Tinkoff-Saxo, at 8 seconds
4. Daniel Martin (Ire) Cannondale-Garmin, st
5. Wilco Kelderman (Ned) LottoNL-Jumbo, st
6. John Darwin Atapuma (Col) BMC, at 11 seconds
7. Domenico Pozzovivo (Ita) Ag2r-La Mondiale, at 15 seconds
8. Alejandro Valverde (Esp) Movistar, at 19 seconds
9. Vasil Kiryienka (Blr) Team Sky, at 21 seconds
10. Rafael Valls (Esp) Lampre-Merida, st
1. Bart de Clercq (Bel) Lotto-Soudal, 18-32-02
2. Richie Porte (Aus) Team Sky, at 21 seconds
3. Domenico Pozzovivo (Ita) Ag2r-La Mondiale, at 26 seconds
4. Daniel Martin (Ire) Cannondale-Garmin, at 27 seconds
5. Alberto Contador (Esp) Tinkoff-Saxo, at 28 seconds
6. Rigoberto Uran (Col) Etixx - Quick-Step, at 45 seconds
7. Fabio Aru (Ita) Astana, at 48 seconds
8. Wilco Kelderman (Ned) LottoNL-Jumbo, at 51 seconds
9. Alejandro Valverde (Esp) Movistar, at 52 seconds
10. John Darwin Atapuma (Col) BMC, at 54 seconds
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