Forget how the hell did a young Australian professional of barely a year by the name of Cameron Davis win the Australian Open, but how the hell did Day lose it?

"It is what it is," Day shrugged after a final round fade-out meant his quest to win a first Australian Open continues. "You're trying to win a tournament regardless of where you are.

"When you hold the lead and everyone's expecting you to win there's a bit of added pressure on that as well. A few bounces here and there. I just didn't play my best. It's not great to shoot two-over par in the final round when you've got the lead.

"It's disappointing not to come out and finish it, but I've got to look at what I need to do better next time because you can't be perfect all the time. I played three terrific rounds and I just didn't put it together on Sunday."

He's not the first and won't be the last. And you didn't need to look at the leaderboard to see that.

There were only two players in the eventual top 15 who shot over par in the final round, Day and his playing partner Lucas Herbert.

Day (-8) finished three shots behind Davis, with Herbert a further shot back. They were supposed be the David and Goliath struggle on the final day, but Sunday does funny things to many people. Including Goliath.

"I had everything clicking the first three days and today was something else," Day said.

"I'm looking forward to getting some time off and decompress and not think about golf because this whole year I've been stressing about how I can get better and better and better - and unfortunately when you worry about playing good you can actually worry too much and force a habit a bit and you don't end up playing good at all."

Day said all sorts of nice things about Herbert on the eve of the final round, yet the greatest compliment was what he didn't say. Saturday's niceties between shots were replaced by Sunday silence between shots.

Just like it did to Matt Jones in the final group of the final round two years ago, the ninth hole at The Australian wreaked all sort of havoc on a man who was supposed to win the national championship. Only difference was Day never recovered.

His second shot from a fairway bunker kissed the top lip of the bunker, spewed left and trickled into a water hazard. He bickered with caddie Luke Reardon over the yardage of his subsequent shot, signed for a double-bogey six and now tournament organisers wait to see if he wants redemption at the first possibly opportunity.

Herbert (-7) had the lead at the halfway point of the final day. By its end he had dropped four shots and could muster only a tie for sixth.

Told it was hard to remember he was still 21, Herbert quipped: "I don't think I'll forget I'm 21 tonight.

"There's too many positives to worry about the negatives at the moment. I burnt a lot on Friday knowing I was playing with Jason on Saturday. Mentally it's so draining being up in the lead because your mind wants to run full stop and flat out. You can't get it to stop. That makes you so tired."

Jordan Spieth? He shouldn't be too tired having come off a six-week break and he might return on Monday to play a fifth round.

Having waited, waited and waited to find his mojo this week, the world No.2 started sinking putts just as the plane was warming its engines to whisk him to the Bahamas for Tiger Woods' Hero World Challenge.

"I told [coach and caddie] Cameron [McCormick], now we're going to start," Spieth (-6) joked after a last hole eagle ensured a top-10 finish. "You have off putting weeks."