Portuguese Nelson Oliveira of the Lampre-Merida team caught his breakaway companions off guard to win the 13th stage of La Vuelta on Friday, while Ireland's Nicolas Roche finished third to continue his strong performance on the third grand tour of the year.
Oliveira jumped away from a group of 24 riders in a descent with 27km remaining and never looked back.
The 26-year-old, his country's time-trial champion, crossed the line one minute ahead of the chasers.
France's Julien Simon (Cofidis) was second and Roche (Sky) took third place at the end of a 178km ride from Calatayud to Tarazona.
Overall leader Fabio Aru of Italy finished safe in the main pack, almost five minutes off the pace, to retain the red jersey.
He still leads Spain's Joaquim Rodriguez (Katusha) and Dutchman Tom Dumoulin (Giant-Alpecin) by 27 and 30 seconds respectively.
A big battle between the top guns looms on Saturday as the 14th stage is a tough mountainous ride between Vitoria and Fuente del Chivo.
Roche moves up to 16th overall, lying 9:38 off the red jersey.