Defending champion Jon Rahm will take a five-shot lead into the final round of the Open de Espana after lighting up the back nine on Saturday.
Rahm started moving day two shots adrift of fellow Spaniards Rafa Cabrera Bello and Adri Arnaus, but took command with a magnificent eight-under 63 in his homeland.
The world number five produced a masterclass after hitting the turn in 35, picking up a further seven shots on the way home at Club de Campo Villa de Madrid to sit pretty on 17 under.
Rahm carded an astonishing back-nine 28 to put himself well on course for a fifth European Tour title and top spot in the Race to Dubai rankings.
The Ryder Cup star dropped shots at back-to-back holes before the turn but got on a roll to move away from his compatriots, gaining a stroke at the 10th to stand just a shot off the lead before reeling off four birdies in a row and an eagle two at 16.
Cabrera Bello and Samuel Del Val share second place on 12 under following third rounds of 70 and 69 respectively.
Three-time European Tour winner Cabrera Bello was bogey-free through his first two rounds, but he dropped a shot on the first and made another two bogeys as Rahm shifted through the gears.
The 1,413-ranked Del Val, who does not have international playing privileges, gathered momentum with three birdies in the space of four holes on the back nine, but dropped one shot on the front nine and another at the 18th.
Arnaus' challenge faded as he signed for a 72, dropping back to a share of fifth place with Jason Scrivener and Zander Lombard, with seven shots to make up on Rahm, while Jens Dantorp is fourth on 11 under.