The bookend birdie runs were offset by four dropped shots through the middle of the round, Luck’s eventual 2-under 68 enough to move him to T20 ahead of Sunday’s final round.
The 20-year-old, who was paired with fellow Australian Geoff Ogilvy for the third round, now leads the Australian challenge after both Ogilvy and Matt Jones shot over par.
Ogilvy signed for a 71 while Jones, who began the day inside the top 25, fell more than 50 places after a 75 that included a quadruple bogey eight at 13th hole of the Old White course.
There were no such issues for Luck who will head to Sunday 10 shots behind leader Sebastian Munoz, the Colombian continuing to dominate on the greens as he opened a two shot lead over American Robert Streb.
Munoz, playing his rookie season on the Tour, is yet to post a top 25 on the Tour but is well on track to break that duck this week.
For Luck the stakes are high Sunday as he attempts to play his way on to the PGA Tour in 2018.
If he can repeat his effort of last week and inch inside the top 10 by tomorrow afternoon he will earn another tournament start at next week’s John Deere Classic and keep alive his chances of possibly earning exemption for next year.
Jones, too, is attempting to earn his card for the 2018 Tour after losing full privileges at the end of 2016.
With only limited starts this year the 2015 Australian Open champion has risen to 132nd on the FedEx Cup but needs to be top 125 to achieve full status.
A fighting second round had Jones in good position heading to the weekend at 4-under and on track to earn vital points but disaster struck on the back nine Saturday to send him tumbling down the leaderboard.
Two penalty shots off the tee quickly led to a quadruple bogey eight at the par-4 13th and dropped Jones from T22 overnight to T67 heading to Sunday.
Ogilvy heads to the final round T54 after a 1-over 71 which included two bogeys and a double.
The 2006 US Open champion has been improving though inconsistent in recent weeks and will be looking for a strong finish tomorrow.