The three-stroke advantage the world No 1 had carved out at halfway after a second-round, course-record 61 was trimmed by one as he bogeyed his penultimate hole at TPC Southwind on Saturday before signing for a two-under 68 and closing on 13 under.
Sam Burns carded a sizzling, bogey-free eight-under 62 while Sungjae Im shot a three-under 67 with those players the leader's closest challengers on 11 under.
- Leaderboard: St. Jude Championship, FedExCup Playoffs
- Latest Sky Sports deals or stream golf with no contract
- Listen to Sky Sports Golf Podcast with Jamie Weir and guests
But Scheffler is now just one good day away from his maiden trophy since The American Express in California at the start of the year, not that he hasn't threatened in that time.
The 30-year-old has recorded five runners-up finishes, including at the 3M Open in his previous event, and nine top-fives in total in the intervening months.
In his third round in Tennessee, Scheffler bogeyed his fourth hole before birdies at two, 11, 12 and 16 preceded that dropped shot at 17, which came after he picked out a left-hand bunker with his second shot at the par four.
Defending FedExCup Playoffs champion Tommy Fleetwood remains in the hunt after a two-under Saturday - the highlight of which was a monster birdie putt at 13 - leaving him five strokes adrift of Scheffler on eight under and in a share of fourth with Jake Knapp.
Rory McIlroy, though, is languishing in tied-67th place on six over - 19 shots off Scheffler - after shooting a two-over 72 on Saturday, with the world No 2 yet to post an under-par round this week.
McIlroy, a three-time FedExCup Playoffs champion, was even par on the day heading to the 18th in his third round, only to then finish with a double bogey after finding the water off the tee.
The 37-year-old picked up back-to-back birdies at nine and 10, while his bogeys came at two and 13 before his gory final hole.
Watch the final round of the FedEx St Jude Championship live on Sky Sports Golf from 4pm on Sunday. Stream golf with NOW.
