Ross McGowan took the biggest 54-hole lead on the European Tour this year after a 12-under 60 on Saturday gave him a seven-stroke advantage at the Madrid Masters.
The Englishman was at 24-under 192 after a third round that included two eagles and 10 birdies at the Centro Nacional course.
"I can't believe it really," McGowan said. "I just played my own game and didn't think about the score until I hit the second shot to the 18th."
McGowan could bolster his Ryder Cup prospects with his first victory of the season. He is currently eighth in the standings.
Sergio Garcia bogeyed four of his last seven holes on his way to a 71 that put him 10 shots back after he shared the overnight lead with David Drysdale. The Scot had a 69 and was eight strokes adrift.
The Spaniard, who is winless this season, started with back-to-back birdies and was only one shot behind McGowan at the turn. Things then fell apart thanks to five bogeys.
Michael Lorenzo-Vera (64) of France and Danny Willett (66) of England shared second place.