Former world number one Ko Jin-young finished a marathon day with a one-shot lead in the LPGA Volunteers of America Classic in Dallas, Texas, on Saturday.
Ko, whose 92-week reign atop the world rankings ended Monday when Nelly Korda ascended to number one, had an eagle and three birdies in a five-under par third-round 66 that gave her a 14-under par total of 199 as darkness fell.
She was one stroke in front of 36-hole leader Matilda Castren of Finland and Germany's Esther Henseleit.
Castren posted a three-under 68 for her 13-under total of 200 while Henseleit stormed up the leaderboard with a seven-under par 64 that featured an eagle and eight birdies.
Ko's day at The Colony started long before her bogey-free third round.
She was among the wave of players who failed to finish the second round after a six-hour weather delay on Friday.
The seven-time LPGA tour winner was even par through four holes when play was halted on Friday, and returned to complete a one-under 70 that left her one stroke behind Castren heading into the third round.
"I couldn't sleep well last night," Ko said after polishing off her second round. "I finished at 8:30 and I got in the bed maybe after 10:00 ... wake up at 4:50 -- so I couldn't sleep well and then I was tired on the course."
It didn't show. After a brief rest at her home in nearby Frisco, Texas, Ko opened the third round with a birdie to promptly join Castren atop the leaderboard.
Ko added a two-putt birdie at the par-five sixth. She and Castren were tied for the lead through nine holes, but Ko pulled ahead with a birdie at the 13th followed by her hole-out for eagle at the par-four 15th.
That saw her jump ahead of Henseleit, who roared up the leaderboard with four birdies in the first nine holes, including a run of three straight at the sixth, seventh and eighth.
A birdie at 13 gave the German a share of the lead but she dropped back with a bogey at 14.
She, too, eagled 15, and added one more birdie at 17.
"I actually didn't think we would get that close to not finishing, but I'm so happy that we did," said Henseleit, a 22-year-old who is seeking a first LPGA title.
The German won the 2019 season ending Magical Kenyan Ladies Open on the Ladies European Tour to scoop that season's Rookie of the Year and Order of Merit awards.
"It really is dark," she said of the late finish. "You couldn't really see the pins on the last two holes. But just happy to be sleeping in tomorrow."
Castren did enough to keep herself in the hunt. She and Henseleit were three strokes clear of South Korean Lee6 Jeong-eun, who finished with three straight birdies in a 69 for 203.
Defending champion Angela Stanford carded a 65 to share fifth with Slovenian Ana Belac (68) on 204.