France's Warren Barguil broke clear in the final kilometre to win stage 13 of the Vuelta a Espana in Castelldefels.
The 21-year-old was involved in a 10-man breakaway in the final 40km of the 169km race from Valls.
The Argos-Shimano rider powered up a short uphill finish to secure his first professional win from Italy's Rinaldo Nocentini and Dutchman Bauke Mollema.
Italy's Vincenzo Nibali finished with his rivals to maintain his 31-second race lead over Ireland's Nicolas Roche.
With three mountainous stages coming up over the weekend, the main contenders were content to conserve their energy and let the breakaway riders contest the finish.
And with more experienced riders such as Michele Scarponi, Mollema and Nocentini keeping tabs on each other, Barguil slipped away to take the victory by seven seconds.
The group containing Nibali and Roche finished two minutes 43 seconds adrift.
Saturday's 14th stage takes the riders 155.7km from Baga to a summit finish in Andorra.
Result of stage 13
1. Warren Barguil (France / Argos) 4:00:13"
2. Rinaldo Nocentini (Italy / AG2R) +7"
3. Bauke Mollema (Netherlands / Belkin)
4. Ivan Santaromita (Italy / BMC Racing)
5. Xabier Zandio (Spain / Team Sky)
6. Amets Txurruka (Spain / Caja Rural)
7. Michele Scarponi (Italy / Lampre)
8. Egoi Martinez (Spain / Euskaltel)
9. Jerome Coppel (France / Cofidis) +24"
10. Benat Intxausti (Spain / Movistar) +2:34"
Overall standings after stage 13
1. Vincenzo Nibali (Italy / Astana) 49:29:02"
2. Nicolas Roche (Ireland / Saxo - Tinkoff) +31"
3. Alejandro Valverde (Spain / Movistar) +46"
4. Chris Horner (U.S. / RadioShack)
5. Joaquim Rodriguez (Spain / Katusha) +2:33"