Brandon Stone fired a third consecutive round of 66 to open up a two shot lead heading into the final round of the Portugal Masters.
The South African has registered just two bogeys all week to get to 15 under and leads the way from countryman Dean Burmester and England's Oliver Fisher.
Fisher carded the first 59 in European Tour history at Dom Pedro Victoria Golf Course last season but entered the week fighting to keep his playing privileges at 112th in the Race to Dubai Rankings Presented by Rolex.
He had to show all of his fighting spirit in round three as he battled back from three over to card a 70 and sit alongside Burmester, who signed for a 65.
Fisher's countryman Steven Brown was at 12 under after a 65 as he battles to save his card, with South Korean Jeunghun Wang and South African trio George Coetzee, Haydn Porteous and Justin Walters a further shot back.
Brown has more work to do if he is to get into the top 115 in the Race to Dubai Rankings Presented by Rolex and guarantee his place on Tour for next season, while Wang and Walters were both provisionally on the right side of the line after 54 holes.
Stone has been making some changes to his game and has just one top ten this season which came over ten months ago at the South African Open hosted by the City of Johannesburg.
He has no concerns over his future, however, and a victory would make it four consecutive campaigns with a European Tour win since he graduated from the European Challenge Tour in 2015.
"I hit the ball incredibly well today," he said. "The irons have really been in tip top shape.
"It was really tricky, the pins are really tucked and I was very fortunate to hole a few putts on that back nine and really put together a nice score.
"I really feel just comfortable in my game and comfortable in my swing."
Burmester chipped in at the first for a birdie and then put his second to four feet on the par five fifth for an eagle to move into double figures.
His tee shot hit the pin on the par three eighth, leaving him a tap-in to get to 11 under, and there was soon a five way tie for the lead at that mark including Stone.
The 26-year-old had bogeyed the third but he picked the shot back up on the fifth and then holed from six feet on the eighth.
Burmester played an incredible bunker shot to set up a birdie on the 12th and hit the front on his own but Stone holed a long left to righter on the 11th to share the lead.
Stone took advantage of the par five 12th to lead on his own but Burmester joined him with a birdie from six feet on the short 15th before he missed the green to bogey the next.
Burmester bounced back with a two putt birdie on the par five 17th but Stone put his tee shot to 12 feet on the par three 16th and two putted the next for another birdie and a two shot lead.
It all looked to be going wrong for overnight leader Fisher as he three putted the fifth and missed the green on the sixth and seventh for three bogeys in a row.
But he made a two putt birdie on the 12th, holed a long putt on the 13th, added another gain on the next and then holed another long putt from the fringe at the 15th to get back into red numbers on the day.
Brown made birdies on the second, fourth, tenth, 14th, 15th and 17th in his bogey free effort.
Walters led by two early in the day but fell back in a level par 71 - a score matched by Wang - while Coetzee signed for a 68 and Porteous recorded a 69.
World Number 29 Matt Wallace, defending champion Tom Lewis, fellow Englishman Eddie Pepperell, Italian Renato Paratore and France's Adrien Saddier were all five shots off the lead.
