Julien Guerrier fired two eagles in three holes to catch halfway leader Jorge Campillo with a brilliant third-round 63 at the Andalucia Masters that left him tied at the top on 19-under-par.
France's Guerrier had already made five birdie in his first 10 holes before firing a sensational second to four feet at the par-five 12th and another to nine feet at the long 14th before making both putts.
Spain's Campillo made four birdies in his 68 as he remained bogey-free for the week, with English pair Dan Brown and Jordan Smith third and fourth on 16-under and 15-under, after matching rounds of 67 in Sotogrande.
Guerrier said after his round: "The key is the short game - it's where I made my score. I hit two great shots on the par fives and a little bit of luck as well; I was not playing exactly there but it finished well.
Tom McKibbin carded a string 69 that left him on seven-under.
"It's not a sprint a tournament it's a marathon so I just try to enjoy every moment."
Campillo made birdies at the second, fourth and seventh as he set about preserving his halfway lead before a superb par save at the ninth, where a wayward drive landed amongst trees and he was only able to bump his approach into the back bunker.
Guerrier completed a hat-trick of gains with a 32-foot putt on the short fourth and added further birdies at the fifth and 10th before his back-nine pyrotechnics saw him claim a share of the lead.
In contrast a tap-in birdie at the 12th was all Campillo had to show for his back-nine efforts despite hitting some excellent approaches as he found every green in regulation on the way in.
Campillo said: "I played quite solid - apart from nine I hit all the other greens so it was stress-free.
"I hit some great shots coming in but I didn't make the putts. I felt I was hitting great putts so hopefully tomorrow I can make some of the putts."
Two-time major winner Jon Rahm has his work cut out on Sunday after a 68 left him seven shots off the lead.
