China's Yin Ruoning shook off her pre-round doubts to fire nine birdies in a nine-under-par 63 on Thursday and share the LPGA Tour Championship first-round lead with Japan's Nasa Hataoka.
Hataoka also nabbed nine birdies without a bogey on a rain-softened Tiburon Golf Club course in Naples, Florida.
The leading duo were a stroke in front of Australian Minjee Lee, with Sweden's Anna Nordqvist a further stroke back on 65.
Thailand's Patty Tavatanakit, England's Georgia Hall, Choi Hye-jin of South Korea, Liu Yu of China and American Alison Lee were tied for fifth, three shots off the lead.
Yin said that warming up in the wind she "didn't feel great about my swing."
Encouraged by her coach, however, she stuck to a basic game plan, hitting every fairway in regulation and taking advantage of her birdie chances.
"I just tried to hit the fairway, hit the green, and just tried to make the putts," she said. "And I'm doing good."
Yin's two victories in 2023 include a major title at the Women's PGA Championship. After trading the No 1 world ranking with Lilia Vu in recent months, she's aiming to end her breakout campaign with one more prestigious victory in the season finale that this year carries a $2 million winner's prize.
It wasn't until after five birdies on the front nine, she said, that she started to think "OK, maybe today is the day. Maybe I can just go for it."
Her last birdie of the day at the par-five 17th pulled her into a tie with Hataoka, the world number 18 who is chasing a seventh LPGA title but her first since 2022.
Hataoka hit 13 of 14 fairways in regulation and said she hit it "really good" with her irons to give herself plenty of opportunities.
Hataoka has gone low before at Tiburon, where she finished runner-up in 2021.
"This golf course has really wide fairways, so stay aggressive," she said of how she's learned to attack the course. "These greens (are) a little bit difficult with grain, but my read is getting better each year."
Lee grabbed solo second with back-to-back birdies at 17 and 18 – rolling in a long birdie from off the green at the last.
"I hit two kind of average shots into the hole," she said. "Probably picked the wrong club on the last, but went a little long and that putt, I think it was just a bonus that it went in.
"It was kind of two different breaks obviously before it got to the green and to the hole, so it was nice to see it go in."
World No 1 Vu had four birdies and two bogeys in a two-under par 70 that left her tied for 32nd.
Vu has enjoyed a breakout year featuring four titles – two of them majors at the Chevron Championship and Women's Open – and came into the season finale leading France's Celine Boutier in the Player of the Year race.
Boutier, whose four 2023 victories include her home major the Evian Championship, had five birdies, but ended up with a double bogey at the par-four 15th after her tee shot hit a cart path and bounced out of bounds.
Her 69 left her tied for 22nd.