The world No. 5 was 1 over par after five holes, but then he got the putter working with birdies on Nos. 6 and 7. He added three more birdies on 12-14, made a bogey on 15, and added one more birdie on the par-5 16th before signing for a 4-under 68.
"I was very proud of how we played after the first five holes," Spieth said. "Very solid back nine, minus one wedge shot, but feel better on the greens, more comfortable on the greens, and got myself back into contention."
Spieth only needed 25 putts on Saturday at Royal Sydney as he looks to win the Australian Open for the second time in three years. Spieth won two years ago at the Australian Golf Club, and he finished one behind Matt Jones in 2015.
"I feel like from Thursday until now I have made a lot of progress," Spieth said. "Each day's gotten a bit better and a bit more comfortable, so hopefully that continues tomorrow."