Scott refused to use the thick blanket of smog hanging over Sydney as an excuse for shooting a 75 at The Australian GC to sit at four-over-par.

The former world No.1 sits a distant 10 shots behind a pair on unheralded amateur leaders, Japan's Takumi Kanaya and Taiwan's Yu Chun-An (65).

Scott's 75 is his worst opening round at the Australian Open since posting the same score to start the 2010 Open at nearby The Lakes GC.

Instead, the 2013 Masters winner at Augusta figures it is competitive rust having not played a tournament since the WGC event in China one month ago.

"I hope so," Scott joked after his round.

A marquee signing for the Open in Sydney before next week's Presidents Cup, Scott's round began ominously with four bogeys on the front nine.

Scott stopped the bleeding with an even-par back nine while he also avoided a birdie-less round - making a 4 on the par-5 18th hole to finish.

Still, Scott's typically flawless swing deserted him at times.

"On the front nine I hit some really bad drives; low left and then I couldn't scramble," he said.

"I got it feeling a little better on the back nine."

But the 13-time US PGA Tour winner is confident of turning it around for Friday's second round on a course he has thrived on in past Opens.

"Oh yeah, absolutely," said Scott, who in his last Open at The Australian finished a shot behind winner Matt Jones (2015).

"I can get off to a good start on the back nine and hopefully, by the end of the day, be in the red figures and start my climb.

"At least now I know where (the ball) is going and I can now chip away at this thing."

Australian Associated Press