A surging Day exorcised some demons to raise hopes of another famous Australian Masters triumph with a stirring fightback on an incredible moving day at Augusta National..
From eight shots back entering the weekend, Day vaulted himself into contention for an elusive green jacket with the lowest third round of his 15-year Masters career, a pressure-filled four-under-par 68.
As the game's biggest names rose and fell around him, the former world No.1 kept his emotions in check beautifully to find himself just three strokes off the lead in a tie for fifth entering the final round.
As runaway halfway leader Rory McIlroy unravelled at Amen Corner, Day peeled off four consecutive back-nine birdies, then remained cool in crisis to climb to eight under for the championship.
After finding the water on the 15th hole and taking bogey, Day's playing partner Cameron Young also showed incredible composure to rebound and close out a scintillating seven-under round of 65 to join McIlroy (73) in a share of the lead at 11 under.
But it was Day's day for Australian fans.
The former runner-up found himself nine shots adrift of McIlroy after making bogey on the first hole - before staging his comeback.
He steadied with birdies on both front-nine par-5s to reach the turn at five under, then hit the go button with four more in a row from the 12th to the 15th holes.
"I was playing with Cam Young today, who is co-leading currently and I was just trying to keep up with him," Day said.
"Obviously he had it going early and I had a pretty average start. I bogeyed the first hole with a three-putt, so you're just trying to steady the ship and just be patient. You know that opportunities will come.
"Statistically, I average around four to five birdies a round, so I just knew they were going to come. I just didn't know when they were going to come."
The 38-year-old rode his luck on No.15, his nemesis hole that has caused so much heartache in seemingly endless previous near-misses.
Going for broke in his bold bid to join 2013 champion Adam Scott as only Australia's second Masters winner, Day's second shot into the par-5 seemed certain to disastrously dribble back into the water.
It didn't and he made birdie and was thanking the golfing gods.
"I was trying to hit this high draw and I mis-hit it, and it stayed out there. I just didn't think," Day said.
"It's difficult because of where the wind, it's swirling everywhere. That's the caddie's worst nightmare. Very fortunate it stayed up."
Not even a bogey on the par-3 16th, when he dragged his tee shot into the bunker and was unable to get up and down, could derail the inspired former PGA Championship winner.
Staring down back-to-back dropped shots, Day's scrambling par from the trees on 17 and another on 18 left the popular US-based Queenslander within striking distance entering what shapes as a final round for the ages.
One of only four players in history to finish runner-up at all four major championships, Day boasts four additional top 10s in his ongoing quest to claim a Masters jacket.
He tied for eighth last year.
Now he merely craves to be in the final-round mix, acutely aware of the old saying that "the Masters doesn't start until the back nine on Sunday".
"You just got to try and get yourself the opportunity on the back side. If you can get somewhere close to the lead on the back side, anything can happen," Day said.
"The goal is to try and cut into the lead tomorrow through nine and, if I can do that, great.
"Then get myself somewhere near the lead on the back side and try and give myself opportunities."
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