Christiaan Bezuidenhout turned in 34 to maintain his four shot lead on day three of the Estrella Damm N.A. Andalucía Masters hosted by the Sergio Garcia Foundation but Jon Rahm made a big move at Real Club Valderrama.
World Number 11 Rahm carded his lowest round of the week with a 67 to get to five under but that was still four back of Bezuidenhout, who made a single birdie on a blemish free front nine.
Japan's Hideto Tanihara was also at five under after 13 holes, two shots clear of Belgians Nicolas Colsaerts and Thomas Detry, South African George Coetzee, Scotland's Scott Jamieson, Frenchman Mike Lorenzo-Vera and Spaniard Alvaro Quiros.
South African Bezuidenhout has two runner up finishes on the European Tour but is still searching for that first win after claiming third place at last week's BMW International Open.
Home favourite Rahm made a big early move, birdieing the fourth and sixth and getting up and down from sand at the eighth to join the group in second.
That group began to swell but it was soon five back as Bezuidenhout - after saving par following a poor tee shot on the first - put his approach to two feet at the second.
Playing partner Quiros had left a chip on the same hole in the rough to drop a shot but he followed up brilliantly, almost aceing the par three next.
Bradley Dredge birdied the fourth to cut the gap to four but dropped shots on the sixth and seventh, while Lorenzo-Vera also got to five under after birdies on the second, fourth and eighth but he bogeyed the ninth and tenth.
Tanihara was quietly going about his business and birdies on the fourth and fifth saw him turn in 33 and sit in a share of second.
Rahm dropped out of that group after missing the green and playing a poor chip on the par three 15th but he was soon replaced by Coetzee.
The four time European Tour winner sandwiched a birdie on the fifth with bogeys on the fourth and sixth but added further gains on the eighth and ninth to turn in 34.
Lorenzo-Vera took advantage of the par five 11th to get back to four under but that remained five back as Bezuidenhout made excellent up-and-downs for par at the seventh and eighth.
Rahm then moved back into the group in second as he hit the 17th green in two and took two putts for a birdie.
He soon found himself in third, however, as Tanihara holed a ten foot right to lefter on the 13th to cut the lead to four shots.
Playing partner Lorenzo-Vera dropped a shot on the same hole to fall to three under alongside Detry, who made an eagle, four birdies, a bogey and a double in a 68.
Quiros joined that group with a bogey on the ninth and Coetzee dropped a shot on the 12th but Rahm was moving in the other direction, holing a 15 footer on the last to set the target.
Colsearts was one under for his round with one to play, while Jamieson was level par through 14.
Thomas Bjørn thought he had missed the cut with a bogey-bogey finish on Friday but the conditions brought the field back to him and the 2018 Ryder Cup captain took full advantage.
The Dane made a hat-trick of birdies from the fourth and, while he dropped a shot on the seventh, further gains on the eighth and 15th handed him a 67 and a two under total.
