Narin An handled the windy conditions with a hot putter on Thursday, making four straight birdies around the turn and finishing with an 8-under 64 for a one-shot lead in the CME Group Tour Championship.
At stake for the 60-player field is a 4 million prize to the winner, the largest single-day payoff in women's golf.
Nelly Korda already has won more than that during her sterling season of seven wins. Now she faces an eight-shot deficit over the next three days at Tiburon Golf Club if she wants to end her year in fitting fashion.
Korda, coming off a victory last week, couldn't make amends for her three bogeys and had to settle for an even-par 72. She has come from behind in four of her victories, and still has 54 holes ahead of her. But it has made the task that much tougher.
Everything felt easy for An, a 28-year-old from South Korea who has never won on the LPGA and has never cracked the top 10 in any of the 16 majors she has played.
