Chris Froome's hopes of winning the Volta a Catalunya were dashed after the Team Sky rider lost 26 minutes on the penultimate sixth stage.
The three-time Tour de France winner could not regain contact with the lead group following an early split in the peloton during the 189.7-kilometre stage from Tortosa to Reus.
The Briton, who started the day just 21 seconds behind leader Alejandro Valverde, plummeted down the leaderboard ahead of Sunday's final stage, which is likely to end in a bunch sprint in Barcelona.
Movistar's Valverde takes a 53-second lead into the 138.7km finale after finishing second on stage six, with Daryl Impey (Orica-Scott) taking victory following a sprint.
Alberto Contador (Trek-Segafredo) moved up to second in the general classification standings, with Great Britain's Adam Yates (Orica-Scott) now fourth, one minute and 21 seconds behind Valverde.