Defending champion Jon Rahm carded an incredible back nine of 28 to take a five shot lead into the final round of the Mutuactivos Open de España.
The home favourite entered round three two shots off the lead and he was still there after nine holes as he turned in 35 at Club de Campo Villa de Madrid.
The World Number Five then made five birdies and an eagle on the way home in a 63 to get to 17 under and lead the way from fellow Spaniards Rafa Cabrera Bello and Samuel Del Val.
Del Val - ranked 1,408 places below Rahm in the Official World Golf Ranking and without playing privileges internationally - bogeyed the last in a 69, while three time European Tour winner Cabrera Bello signed for a 70.
Swede Jens Dantorp was then at 11 under, a shot clear of local favourite Adri Arnaus, South African Zander Lombard and Australian Jason Scrivener.
A victory for Rahm would see him make it five European Tour wins from just 39 appearances, including three Rolex Series victories, while a top four finish would move him to the top of the Race to Dubai Rankings Presented by Rolex.
The 24-year-old has often spoken of all Spanish golfers walking a path created for them by the late, great Seve Ballesteros and Rahm could reach five wins in ten fewer events than his hero at the venue where Ballesteros claimed his 50th and final European Tour victory 24 years ago.
"I've never teed up with such a lead," he said. "Every time I've teed off it's been a one shot lead or tied for the lead so it's going to be a little bit of a different story.
"I don't know what the challenge is going to be. I have a real good chance to defend this title, I'm feeling good so hopefully I can keep doing what I've been doing.
"It's just one of those days where everything was going good for me on that back nine."
Rahm put his tee shot to ten feet at the par three third and got up and down from the back of the par five next before another up-and-down handed him the solo lead on the seventh.
Back to back bogeys on the eighth and ninth had him two shots off the lead but then - just a week after Justin Rose carded the second 28 of the season for nine holes - Rahm produced something special.
He holed from 18 feet on the tenth and stunning approaches to the 12th and 13th left him less than five feet for birdie and moved him into a two shot lead.
An up-and-down from sand on the par five 14th for another gain and an approach to six feet on the 15th made it four birdies in a row and maintained the leader's three shot cushion.
Del Val had turned in level par with a birdie on the fourth and bogey on the next but he put an approach to tap-in range on the 12th, produced an excellent chip to set up a birdie on the 14th and chipped in on the next.
That cut the lead to two but Rahm was unstoppable and his second from the fairway at the 16th took a hop right and spun into the hole for an eagle, before a Del Val three putt on the last left him five ahead.
Cabrera Bello struggled for momentum throughout the day, turning in level par with birdies on the fourth and sixth but bogeys on the first and fifth before he dropped another shot on the tenth.
An approach to four feet on the 13th and excellent tee shot on the par three 17th then got him back into red figures for the day.
Dantorp made just five pars in a roller coaster of a 65, the highlight being a long putt for eagle on the 14th to go with eight birdies and four bogeys.
Scrivener carded a 68, one shot better than Lombard, while Arnaus slipped back with a 72 that left him two shots ahead of Dane Joachim B Hansen, South African Justin Harding, Japan's Masahiro Kawamura and Paraguay's Fabrizio Zanotti.
