Brandon Stone carded a second consecutive round of 66 to set the clubhouse target on day two of the Portugal Masters.
The South African was bogey free as he made five birdies to move to ten under and lead the way by one shot from England's Eddie Pepperell.
Stone's only top ten of the 2019 Race to Dubai came over ten months ago at the South African Open hosted by the City of Johannesburg and he arrived at Dom Pedro Victoria Golf Course 148th on the Race to Dubai Rankings Presented by Rolex.
Unlike many this week, being outside the top 115 does not put his playing privileges in jeopardy, and Stone was showing glimpses of the sort of form that has made him a Rolex Series champion with wins in every season since graduating from the European Challenge Tour in 2015.
After an encouraging start last time out at the Amundi Open de France, five of his last six rounds have now been in the 60s, and a victory this week would see him play his way into the field for the Turkish Airlines Open.
Pepperell - who also fired a bogey free 66 - has mixed memories of Vilamoura after losing his card here in heartbreaking fashion three years ago.
Entering the week at 110th on the Race to Dubai Rankings Presented by Rolex with the top 111 keeping their cards, he made a double bogey on his 36th hole to fall from the cut line and found himself heading to Qualifying School.
Since regaining his playing privileges at the first time of asking, he has claimed two European Tour victories and finished third here in 2017 before coming second last season.
South African George Coetzee carded a 65 to sit at eight under, a shot clear of countryman Dean Burmester, local favourite Tiago Cruz and Frenchman Adrien Saddier.
Stone birdied the tenth and 17th to get within one of the lead and when he made another gain on the next to turn in 33, he was alongside countryman Louis de Jager.
Pepperell had also made a gain on the tenth and after another birdie on the 15th, he eagled the par five 17th to make it a three way tie.
Stone put an approach to 15 feet on the second to take the solo lead and did very well to make par on the next, getting up and down after finding sand off the tee and leaving his second in the bunker.
Pepperell had no such troubles on the par four, holing from 18 feet to join Stone at the top of the leaderboard.
But the 26-year-old was not in the mood to be caught, and he rolled home a 12 footer on the eighth to become the first player this week into double figures.
Coetzee endured a roller coaster, sandwiching a bogey on the 13th with birdies on the tenth, 12th, 15th and 17th and, when he holed his second on the par five next, he was the nearest challenger.
Bogeys on the first and third sent him tumbling back but he birdied the fourth, holed from 20 feet on the fifth and added another gain on the seventh in an excellent recovery.
Overnight leader De Jager was among the afternoon starters and he parred his first five holes to sit alongside Coetzee.
