Back in Australia for the first time in seven years, Day missed a short birdie putt on his last hole to settle for a bogey-free, four-under 67 at Royal Queensland on Thursday.
Elvis Smylie (65) had the early clubhouse lead, the son of former tennis star Liz chipping from one greenside bunker to another before holing his next shot to birdie his last hole.
"I didn't touch the green and made four, so a pretty good way to finish," he smiled post-round.
Elvis Smylie and his caddie have a laugh after chipping in for a birdie on the 9th. (Dave Hunt/AAP PHOTOS)
Swiss talent Joel Girrbach was a shot further back while Smith, Marc Leishman and South African young gun Aldrich Potgieter were in a group of players two behind Smylie.
Defending champion Min Woo Lee (68) cut a frustrated figure, limping home after carding four birdies in his first six holes playing alongside Smith and Day.
Brisbane had been hammered by rain all week but it eased on Wednesday night as course staff worked overtime to drain bunkers and ensure the fairways weren't water-logged.
Hundreds negotiated the early start and grey skies to see the Australian super-group's 6.10am tee off, a devoted gallery that grew to thousands by the time they finished their round.
We love seeing you home — PGA of Australia (@PGAofAustralia) @JDayGolf 🇦🇺�#AusPGA pic.twitter.com/OlNGtfTJUUNovember 21, 2024
Queenslander Day admitted he wasn't sure how he'd be received given his seven-year absence.
But the former world No.1 was embraced as he enjoyed a rare competitive grouping with Smith, who counted him as one of his idols when the pair were dominant Queensland juniors.
"A little disappointing to not birdie the last there," Day said.
"I managed the round very well (after) three and a bit months off, it was that was a nice round.
"It's fun, you know, it's only going get you know, bigger and better as the week progresses."
Crowds have flocked to watch Jason Day in his first Australian appearance in seven years. (Dave Hunt/AAP PHOTOS)
Smith's radar was slightly off as he mixed two bogeys with two birdies to round the turn even par, before birdieing the first two holes on his back nine in the $2 million tournament he's won three times in the last six years.
He joked that the 3am wake-up time had meant he wasn't truly firing until he rounded the turn.
"The body takes a little bit of time to wake up, and just a couple of lazy swings, particularly at the start, the ball's not going that far," he said.
"It just wasn't all clicking and probably a bit of extra time was the biggest thing.
"After the way I putted last Sunday (at the NSW Open), seeing the ball go in and getting a little bit of confidence, that was nice.
"When I feel like I'm putting good I feel like the rest of my game frees up and I can really start to play some aggressive golf."
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