Seven days after snatching the lead at the Australian Masters and eyeing off the gold jacket, Millar was left lamenting "crazy, crazy mistakes" as he slipped down the Australian Open leaderboard on Saturday.

The Gold Creek Country Club training professional is well out of contention for the Stonehaven Cup, dropping to a tie for 61st after his five-over-par round at The Australian Golf Club.

He sits at eight-over par going into the final day, with Matthew Jones clear in the lead at 10-under and world No. 1 Jordan Spieth lurking just behind at seven-under.

So instead of challenging for winning honours, Millar's focus has switched to finding the rhythm that led to him becoming the surprise leader in Melbourne last week.

"There were way too many mistakes – crazy, crazy mistakes – that just did all the damage," Millar said.

"I was making bogeys from good positions. I was hitting poor shots, not into the water but just ones that you're thinking, 'what are you doing?'.

"I think it's more tiredness than anything. I've been in play and making bogeys from positions I shouldn't be. This is my fourth week [of golf] in a row and I've still got two more to go."

Former Royal Canberra member Ryan Ruffels is two shots ahead of Millar going into the final round.

Millar has made 10 birdies in his three rounds, but they've been cancelled out 13 bogeys and two double bogeys.

Millar has enjoyed a stellar season, with nine top-10 finishes helping him rise to fifth on the Australian Order of Merit.

He is also in contention to win the Australasia player-of-the-year prize at the Greg Norman Medal at Royal Pines on Tuesday night.

Languishing near the bottom of the leaderboard has done little to dent Millar's confidence, adamant he can turn things around in time for the Australian PGA Championships next week.

Millar was in the box seat to claim the gold jacket at the Australian Masters last week as he went into the final round with the lead. But he failed to fire on the final day and missed his chance to claim a huge title.

"I just wasn't feeling it this week. The confidence hasn't really taken a hit," Millar said.

"When I [got to Sydney] I thought my biggest problem at the Australian Open would be making birdies. But I've made 10 in three rounds which is not bad. Somehow I've managed to give away 18 shots."