Britain's David Millar, of the Cofidis team, won the 17th stage of the Tour of Spain on Wednesday.
Millar broke away on the Alto de San Jeronimo climb close to the end of the 188.4km stage between Granada and Cordoba and won by more than half a minute.
It is the third time Millar, who has also twice finished second this year, has won a stage in La Vuelta.
Spaniard Isidro Nozal, who rides for the ONCE team, maintained his overall lead.
Millar told Spanish television: "I planned to be in good shape for the last week of the Vuelta, but I'm better than I expected."
Millar said the victory would give him a boost before the world championships in Hamilton, Canada, next month.
"My big objective for the year are the world championships," he said.
"I love racing here and for me it has been an ideal opportunity to get some good racing and to prepare for the worlds."
The Scot is competing in the last of the three Grand Tours - following the Giro d'Italia and the Tour de France - in a bid to hone his competitive edge
ahead of the World Championships in Canada next month.
1. David Millar (GB) Cofidis, 3 hours, 58 minutes, 2 seconds
2. Alberto Martinez (Spa) Euskaltel, 0:36 behind
3. Oscar Sevilla (Spa) Kelme, same time
4. Unai Osa (Spa) iBanesto.com, same time
5. Michael Rasmussen (Den) Rabobank, same time
6. Erik Zabel (Ger) Telekom, 0:41 behind
7. Fred Rodriguez (US) Saunier Duval-Vini, same time
8. Angel Edo (Spa) Milaneza, same time
9. Tom Boonen (Bel) Quick Step, same time
10. Giovanni Lombardi (Ita) Domina Vacanze, same time
1. Isidro Nozal (Spa) ONCE, 58 hours, 11 minutes, 53 seconds
2. Igor Gonzalez De Galdeano (Spa) ONCE, 3:03 behind
3. Roberto Heras (Spa) US Postal Service, 3:09 behind
4. Manuel Beltran (Spa) US Postal Service, 5:16 behind
5. Alejandro Valverde (Spa) Kelme, 5:20 behind
6. Francisco Mancebo (Spa) iBanesto.com, 6:27 behind
7. Michael Rasmussen (Den) Rabobank, 7:29 behind
8. Luis Perez (Spa) Cofidis, 8:51 behind
9. Unai Osa (Spa) iBanesto.com, 8:57 behind
10. Felix Cardenas (Col) Labarca 2, 9:28 behind