The World No. 2 fired rounds of 70-71-70-67 at The Australian Golf Club in Sydney to finish at six under and five shots behind eventual winner Cameron Davis.
Starting the day eight shots behind overnight leader Jason Day and in need of a Sunday miracle, Spieth birdied two of his first five holes to spark hopes of a charge but played his next eight holes in one over before a birdie at the par-five 14th.
At the par-five final hole, Spieth fired his approach to the back edge of the green and rolled in his nine-foot eagle putt, well aware it was a case of too little too late.
“I really felt like I shot 62 today and it was 67, I had so many looks,” Spieth told the media shortly after his round.
“I’m playing beautifully, the putter felt great today, I found a nice trigger and I was getting through my putts a lot better than I was at the beginning of the week, and had that happened the whole week, I would definitely have been in contention.”
Spieth drives off the 10th tee during Sunday's final round.
The 24-year-old said he struck the ball better this week than he did during his previous two Australian Open victories.
Unlike his wins in 2014 and last year, Spieth had his swing coach, Australian Cam McCormick, caddying for him this week and said the experience will improve their long-term player-coach relationship.
“I think he has more respect for Michael [Greller] and how difficult it is to caddie,” the American said referring to his regular bagman Greller.
“[Cam] said his hips were hurting a lot and just judging the cross winds and trying to be confident in your decisions, but also protecting, I think he learnt a lot about how difficult it is for anybody to caddie on a professional tour.”
Spieth will tee it up next week in the Bahamas in what will be a very small sideshow amid the competitive return of Tiger Woods at his own limited field event, the Hero World Challenge.
“The game feels good, so I’ll get in there and having Cam see pretty much all the swings that I hit on the range and on the golf course, and all the putts, I have that kind of extra confidence that I know where things are throughout the swing. So it should be easy, I shouldn’t have too many questions next week, which will be nice.”
As for making a return to Australia for the fifth straight year in 2018, Spieth remained open to the idea yet non-committal, despite continuing to publicly declare his affinity for Sydney as a city.
“I’d love to explore it. It’s just a matter of, like I’ve said every year, I try and figure out what’s going on the next week, let alone a year from now.
"I’ve been, I think pretty open the last few years in what I’ve been saying and exploring all options into this off season and certainly this kind of off season, the way I did it this year has been very successful for me in the past.”
CAMERON DAVIS' WINNER'S PRESS CONFERENCE
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