Fellow American Collin Morikawa failed to close the gap on Scheffler in Saturday's third round, making a 4-under par 67 at East Lake Golf Club, Atlanta, while Scheffler posted a 5-under round of 66.
The Masters champion and Olympic gold medallist, Scheffler began the week on 10 under-par under the staggered scoring system used for the season finale which determines the FedEx Cup play-off winner.
The system is designed to ensure an advantage for the leader in the Cup standings while still leaving opportunity for challengers should the leader slip up in the final of the three play-off tournaments.
But Scheffler, with his eye on a seventh win on the PGA Tour this season, has shown no signs of opening the door. Morikawa, who began the week six strokes behind the favourite, has managed to reduce the gap by just one shot over the three rounds.
Scheffler offered a glimmer of hope when he bogeyed the par-4 first hole, where after driving into the rough to the right, he missed a 12-foot par putt.
But that was the only blemish on the 28-year-old's scorecard and the finish to his round - with birdies on four of the last five holes, including the last three - sent a clear signal of his intent for Sunday.
"Keep doing what I've been doing, staying in the moment, staying patient out there. I've bogeyed the first hole two of the last three days and both times I didn't make any bogeys after that. So that's kind of good momentum for me," said Scheffler.
"I feel like I've done a lot of stuff well and played solid, so I'm looking forward to the challenge of trying to finish off the tournament tomorrow," he said.
Morikawa had to wait until the par-5 sixth hole for his opening birdie but cancelled it out with a bogey on the next hole.
But he also finished strongly with three birdies from the 15th onwards including the 17th and 18th.
"Solid. Not exactly the moving day that I needed, but I knew this entire week I was going to need something special to come out on top and I'm going to need something very special," said Morikawa.
"It's going to be very hard, but I believe in myself that I can do it. Five shots is a lot, but two-shot swings happen. I think I've seen a couple over the past few days," he added.
"I've got to go low. I know that. Hopefully I've got that in me today. I've got 18 holes left to the season. I keep talking about that, but I'm going to put everything I have into these next 24 hours," he added.
Sahith Theegala is in the third place but nine shots behind Scheffler and his bid wasn't helped by a two stroke penalty on the par-4 third.
The American himself called in the rules official after he saw the sand move before his shot from a fairway bunker.
"I felt like I moved a few grains of sand for sure. In my peripheral, I thought I saw some of the sand move as I took my backswing," said Theegala, who didn't feel he gained any advantage from the sand movement which he described as "insignificant".
"But unfortunately the rule is it doesn't matter the intent. If you change the lie in the direct area around the ball that could affect your swing, it is a two-shot penalty," he added.
Theegala did recover from that setback in some style however as he finished his round with five straight birdies.
Xander Schauffele, the British Open and PGA Championship winner this season, is in fourth place, 10 shots behind Scheffler after his even-par 71, while Wyndham Clark and Australian Adam Scott are 11 strokes off the lead.