The 24-year-old American had struggled to a five-bogey one-under-par 70 in the afternoon winds on Thursday but his plans to make a move in calmer conditions on Friday morning fell flat as his usually reliable putting game failed him.
Only a long birdie putt at his final hole for the second day in a row saved a par 71 for the three-times major champion, who mixed a birdie with a bogey on his front nine and dropped another shot at his 13th.
"It just was a bad day with the flat stick, it happens," said Spieth, who is coming off a seven-week layoff.
"I was a little tentative to start, the greens were slower than I thought I could do on them and I left everything just a foot or so short. If I'd made one of those earlier, it could have been a completely different story today.
"I'm going to look to make a putt early in the round tomorrow and maybe jump-start a weekend like two years ago or three years ago."
At one-under for the tournament, Spieth is likely to have to make up at least nine shots on the leader over the weekend.
Spieth's triumph last year was achieved at Royal Sydney but the Texan also won the tournament in 2014 and finished in a share of second in 2015 on his last two visits to The Australian Golf Club.
Given he will have an earlier start than the leaders on Saturday, he felt the course was tailor made for a weekend charge.
"On this golf course more than just about any that we play, I feel like you can make up more ground and come from behind here over I think any tournament I’ve played this entire year," he said.
"Just given the golf course will start to bake out and you get really calm conditions in the morning that leave the windier conditions for the afternoon.
"So I'll have a pretty gettable golf course I imagine in the morning tomorrow with the guys really having to watch themselves in the afternoon and if I can post something like five, six-under, then I’m very much in this tournament."
(Editing by Peter Rutherford)
