Jin Young Ko of South Korea, who played her way into this week's LPGA season finale with just three starts in 2020, moved to the top of the leaderboard thanks to a bogey-free 67 at the CME Group Tour Championship in Naples, Florida.
The 25-year-old Ko, whose 2020 LPGA season began with the Pelican Women's Championship last month, posted five birdies and no bogeys at Tiburon Golf Club to move to nine-under 135 and grab a one-shot lead over fellow country woman and defending champion Sei Young Kim (69) and first-round leader Lexi Thompson (71).
"It was different conditions today, of course, with the cooler weather in the morning, and I would say overall it was a lot breezier throughout the day," said Thompson, the 2018 champion, who started the day with a one-shot lead but managed just three birdies to combat two bogeys.
"It was a little bit of an up and down day," she added.
"I thought I struck it really well on the front nine. I got a few bad breaks with a few ridges on the greens, but you can get that on this golf course."
Leona Maguire now leads the Irish challenge after she carded a 72 to move up to one over, 10 shots off the lead.
The Cavan native endured consecutive bogeys on three and four, but birdies on nine and 18 helped her to finish with a level par round.
However, Northern Ireland's Stephanie Meadow, who scored a 70 in round one, slipped back down to two over after a 76 which included a double bogey on the second and bogeys on 11 and 17.
However, both players will be involved in the weekend rounds as there is no cut for the 72-player field, who all have an equal chance at the $1.1 million winner's prize, the largest in 2020
Kim, who started the day tied for third, got off to a strong start with four birdies over her first five holes, but dropped two shots with bogeys at seven and nine. She failed to get any momentum back after the turn, carding eight pars and a single birdie at 14.
Australia's Hannah Green, who shot 68, sits alone in fourth place at seven under. Six players are tied for fifth at six under - Nelly Korda (66), Cydney Clanton (68), Austin Ernst (69), Megan Khang (71), Britain's Georgia Hall (69) and Germany's Caroline Masson (71).
Australia's Lydia Ko, who started the day two over, finished on five under and tied for 11th after posting a bogey-free 65. Her seven-under round was the low score of the day and featured seven birdies including three straight to close out her round.
"Yesterday I had enough of my game and my golf," said Ko, the 2014 champion who also holds the 18-hole scoring record at Tiberon (second-round 62 in 2016).
"I told (my caddie) and my mom, 'I'm going to get out of here,' and I just left, and I ordered like five people's worth of food... Like today just came in saying, 'I'm going to try and play the best I can with a lot of confidence,' and I was. My irons and the shots going into the greens were really good, so set up a lot of birdie opportunities. I was able to make a few of them, so, yeah, much better position going into the weekend."
Denmark's Nanna Koerstz Madsen, whose 66 on Thursday was one of just four bogey-free rounds in round one, could not maintain her first-round pace and fell out of contention after shooting 77.
