The 33-year-old had a mixed front nine with three birdies and two bogeys before the turn, but having picked up another shot at the par-four 13th, he birdied the last to remain on course for a third PGA Tour win.
"'Leish' is playing spectacular; he's going to be very hard to beat tomorrow", said Day, who went wire-to-wire during his 2015 BMW Championship win. "I thought with the pin locations, looking at them this morning, I felt there was an opportunity to shoot a low score, which there was".
"It's been, I think, 10 years since the last time I had a hole-in-one". Very easy to throw a mediocre round in there. He's seen me hit a boatload of shots.
"If I have a really good off-season and prepare and practice on the right things, come out mentally fresh and physically fresh, I feel like '18 will be a really good year for me. It sets up nicely for me". He's hitting it in the right spots, hitting it on the greens and holing putts.
Day made a hole-in-one Friday for his third eagle of the week at Conway Farms in his round of 65.
Day was just two-under for the day heading to the par-five 14th, but chipped in for eagle to ignite what would prove to be a stunning finish. "I just knew regardless of what I did, I was going to play well". "It certainly took a few holes for me to adjust to it and I didn't quite have the stuff". "That's a good formula for success and it's going to be tough tomorrow". Although it was a shocking move, Day seemed to suggest that he was blaming Swatton for his poor play, even though he knew otherwise. He failed to convert putts from approximately six feet away on consecutive holes on the back nine.
Leishman is projected to jump to fourth in the standings if he wins on Sunday, behind Americans Justin Thomas, Jordan Spieth and Dustin Johnson.
Fellow Australian Day (5/1), Charley Hoffman (16/1) and Jamie Lovemark (25/1) were his nearest challengers on seven under, while Fowler (7/1) lies in the group a further shot back after birdieing six of his final seven holes.
During NBC's telecast Saturday, Jim Mackay, Phil Mickelson's former caddie who now works as an analyst, called Leishman, "the most underrated player in golf". He sits at 9 under for the tournament.