Belgium's Tim Wellens took the overall lead on the Ruta del Sol after winning Saturday's penultimate stage as Chris Froome's race was ruined by a late puncture.
Most of the attention on the five-day race has been focused on Briton Froome, with the Team Sky rider competing for the first time this season, and the first time since the revelation of his abnormal doping test at last year's Vuelta a Espana.
But the four-time Tour de France winner, having started the day in seventh place and 28 seconds off the pace, saw his hopes of victory evaporate as he suffered a late puncture on the 195km stage that started in Seville.
That also briefly held back his team-mate Wout Poels, who started the day in the overall leader's red jersey.
Wellens, of the Lotto-Soudal team, beat Spain's Mikel Landa, the Movistar leader, and Denmark's Jakob Fuglsang on the tough uphill finish at Alcala de los Gazules, near Cadiz.
He now sits seven seconds ahead of Landa and 11 seconds clear of Dutchman Poels going into Sunday's fifth and final stage, a 14.2km individual time-trial around Barbate, near Cadiz.