LPGA rookie So Mi Lee of South Korea piled up eight birdies to shoot a 6-under 66 and take the first-round lead at the Mizuho Americas Open on Thursday in Jersey City, N.J.
Lee has a two-shot lead over four players tied at 4-under 68, including Australian rookie Gabriela Ruffels.
Lee was the second alternate in the field and was not expecting to get the green light to compete this week.
"At first I was kind of depressed and I think I can't play well today," Lee said. "I also get caddie to go home and we have no caddie, so my father play with me and that made me comfortable playing. Yeah, he was very great."
Lee, 25, started her day on the back nine at Liberty National Golf Club and opened with a birdie at the par-5 10th hole. She made her move with a stretch of four birdies and one bogey at Nos. 13-17 before adding a bogey and three birdies on the front nine.
"At first it was so windy when I was playing first, but second shot was very great," she said. "My second shot was very great, and ... the putting was getting along with my shot."
Ruffels was the only player 4 under or better to go bogey-free on Thursday. She birdied three of her first eight holes before adding one on the back nine.
Ruffels, 24, said she feels she's "definitely getting more comfortable" as her rookie season wears on.
"I feel like the confidence definitely goes up when you have a few good results and I've been fortunate to have a few good results this year, few top-fives and one last week," Ruffels said.
"... But still kind of feel like a rookie. Kind of learning all the new courses. These girls have already seen they courses, but I'm lucky I have a pretty experienced caddie."
Joining Ruffels at 4 under were Bianca Pagdanganan of the Philippines, Japan's Mao Saigo and Andrea Lee.
Major winners Jennifer Kupcho, Thailand's Patty Tavatanakit, Celine Boutier of France, Minjee Lee of Australia and Ashleigh Buhai of South Africa are part of a large tie at 3-under 69.
Nelly Korda opened with a 2-under 70. She is coming off the end of a five-start winning streak on tour, having finished tied for seventh at last week's Cognizant Founders Cup.
Rose Zhang – the 20-year-old phenom who won her professional debut at last year's Mizuho Americas Open and also won last week – withdrew Thursday due to illness.