Australia's Hannah Green must halt American teenager Yealimi Noh's fairytale charge to win the LPGA Tour's Portland Classic after squandering a big halfway lead.
Major-winner Green was five shots clear entering the third round after blistering opening scores of 64 and 63 but she stumbled to a one-over 73 on Saturday to fall back to second place.
Monday qualifier Noh, 18, produced a flawless 64 with eight birdies to claim a three-shot lead after pulling off a nine-shot swing against the 22-year-old Aussie.
Green is two shots ahead of Canada's Brooke Henderson (67) and American Brittany Altomare (68).
Green and Noh will go head to head in the final group on Sunday.
Noh turned down an offer to play for UCLA and instead turned professional in February. She is playing just her seventh event on the tour this year.
She was asked what a Sunday victory would mean.
"It would change my entire like, year, my life," she said. "That would just be a dream come true."
Noh was reminded that Henderson won the Portland Classic as a Monday qualifier in 2015. The only other Monday qualifier to win on the tour was Laurel Kean, at the 2000 State Farm LPGA Classic.
"That would be really, really cool. She (Henderson) is doing so well right now," Noh said. "That's just really cool, Monday qualifying and winning, but I don't want to think about that tomorrow.
"I'll just go out and play my game, but really hope that's the result."
The Portland Classic started in 1972 and is the tour's longest running non-major event.