Brandon Stone turned in 33 to maintain his two shot overnight lead as the Portugal Masters moved towards a tense finish at Dom Pedro Victoria Golf Course.
South African Stone was looking for a fourth European Tour title but many in the field were looking to keep their playing privileges for 2020.
At the start of the week, the top 117 in the Race to Dubai Rankings Presented by Rolex were set to maintain their cards but that mark had moved to 115 in the closing stages on Sunday afternoon.
Hugo Leon was three under for the day and ten under for the week with one to play to provisionally sit in the final spot, with Min Woo Lee and Niklas Lemke facing a trip to the Qualifying School.
At the top of the leaderboard, Stone had moved to 17 under to lead the way from Justin Walters, who had picked up four shots in his first 11 holes and was on course to safely stay on Tour having started the week 121st on the Race to Dubai Rankings Presented by Rolex.
England's Chris Paisley was the clubhouse leader at 14 under, alongside countrymen Steven Brown and Oliver Fisher, who had completed ten holes.
Fisher quickly cut the lead to one with an approach to tap-in range at the first but Stone's response was sensational.
The 26-year-old played a wonderful bunker shot on the second to re-establish his 36 hole advantage and then hit a stunning approach into the third to move three ahead.
Fisher kept some pressure as on as he got up and down from a bunker on the par five fifth but Stone repeated the trick and the lead was back to three.
Stone made a first bogey of the day when he missed the green at the par three sixth but his lead was back to three as Fisher was forced to lay up after narrowly avoiding the water on the par four seventh.
Fisher was replaced in second by Walters who turned in 32 as he took advantage of the fifth, holed from 12 feet on the seventh and made a tricky left to righter on the ninth.
He then found himself in sand off the tee at the tenth but played a wonderful second for another gain.
Brown had birdied the second and holed an excellent left to righter on the ninth but still had work to do to keep his card.
Paisley was bogey free in his round, making gains on the first, fourth, eighth, ninth, 12th, 14th and 15th.
George Coetzee was 13 under with seven holes to play, with Jack Singh Brar in the clubhouse at 12 under having got himself the right side of the line with a 66.