Kiwi Lydia Ko has stretched her lead lead to five shots halfway through the LPGA Tour Championshp at Naples, Florida, after second-round challengers fell away at the Tiburon Golf Club.
Ko held a one-stroke lead over her nearest rivals after the opening round, but Japanese Nasa Hataoka made a red-hot start to her day, birdying four of the first seven holes, and eventually edging ahead with consecutive birdies on the 12th, 13th and 14th.
But back-to-back bogeys on the next two holes saw Hataoka slip from the front, while consecutive birdies on the sixth and seventh carried Ko into a two-stroke advantage, before two more at the 10th and 11th saw her put distance on her opposition.
Her momentum continued, as she picked up shot at the par-five 14th and 17th, and carded a six-under 66 for the day for 13-under after 18 holes.
Korean Hyo Joo Kim finished strongly for 69 to hold outright second, while Hataoka finished with 67, sharing second with world No.1 Nelly Korda, Swede Anna Nordqvist and Scot Gemma Dryburgh, all at eight-under.
The Kiwi made a steady start, with five consecutive pars, as Korda and American Danielle Kang also pulled even over the front nine holes, but she moved back into outright second with her first birdie at the sixth and then passed the faltering Hataoka with another at the seventh.
After bogeying the opening hole of her opening round, the world No.3 rattled off eight birdies - including four straight on the back nine - to card a seven-under-par 65 and emerge ahead of Thai Pajaree Anannarukarn and American Danielle Kang, with Korda lurking a shot further back.
"Not the start that I had envisioned going to sleep yesterday, but I knew that there was plenty of golf to be played," she said.
"No matter what circumstances, I think with the wind being up today, it was going to be a tough stretch of holes to start, so I wanted to not get too caught up with how I started and stay patient out there.
"I think that's going to be a big key this week. It's 72 holes, the LPGA's top 60 players are here this week, so you know there's going to be so much good golf.
"You're just trying to play as good golf as the others."
The tournament carries a US$1.5 million purse, with Player of the Year honours and the Vare Trophy for scoring average - which Ko won last year - on the line.
Ko, 25, won this event in 2014 as a teenager and is coming off her 18th tour win - her second this year - at the BMW Ladies Championship in South Korea.
"I think when you come to a golf course where you've played for quite a bit, you are able to gauge that you're going to have some of those good days and bad days, but I'm hoping to kind of bring it all together,” said Ko.
"The last time I won here was in 2014 - nine years ago - and a lot of things have happened since then. I think the level of play has kept getting better and better in my time on tour, so I know that if I did exactly the same thing, I may not be the one holding the trophy in the present."
Ko and Anannarukarn were due to tee off for the second round at 6:40am Saturday (NZ time).
Follow Ko's progress with us throughout the morning.