Los Angeles - Gerina Piller fired an eight-under par 63 on Thursday to take a one-stroke lead over newly-crowned US Open champion Park Sung-Hyun and Chien Pei-Yun after the first round of the LPGA Marathon Classic in Ohio.
Piller, chasing her first LPGA title, got off to a strong start at Highland Meadows, with birdies at the first three holes and four of the first five.
Another birdie at the par-three eighth was followed by her lone bogey of the day at the ninth and had her making the turn at four-under. She added four more birdies coming in.
"I feel like any time you shoot eight-under is pretty good," Piller said. "Got off to a good start and got the putts rolling. To be honest, my ball-striking didn't feel as great coming into this weekend, and the week after a major it's always tough just because you're so exhausted mentally.
"I just went out there and really trusted what I had and just brought it together."
South Korea's Park, who made her first LPGA win a major championship when she lifted the US Women's Open at Trump National in New Jersey, showed no sign of a let-down as she fired seven birdies in a bogey free round, while Taiwan's Chien had eight birdies in a bogey in her 64.
"My feeling today was awesome," Park said. "It was a good start after winning the major championship."
Park said there was no temptation to dwell on her Open victory, as satisfying as it was and she was focusing on this week's tournament with last week's happiness "behind from now on".
Three players shared fourth on six-under 65: India's Aditi Ashok, South Korean Kim In-Kyung and American Kelly Shon.
Defending champion Lydia Ko, the former world number one seeking her first win since lifting this trophy last year, opened with a two-over 73 that included three bogeys and one birdie.
Ko is seeking a third win in this event, but a return to the course in Sylvania, Ohio, provided little relief from the inconsistency that has dogged her this season.
"When you're not hitting the ball fantastic, it's not going to be the greatest score," Ko said. "But there's always tomorrow.
"I shaped my drivers pretty well, but the three times that I missed a fairway I wasn't able to make up-and-down from there. Hopefully I'll be able to hit a few more fairways."
Leading first-round scores on Thursday in the LPGA Marathon Classic at Sylvania, Ohio (USA unless noted, a-denotes amateur. Par 71)
63 - Gerina Piller
64 - Chien Pei-Yun (TPE), Park Sung-Hyun (KOR)
65 - Aditi Ashok (IND), Kim In-Kyung (KOR), Kelly Shon
66 - Angel Yin, Sandra Changkija
67 - Lexi Thompson, Alison Lee, Feng Simin (CHN), Thidapa Suwannapura (THA), Dori Carter, Chella Choi (KOR), Brittany Lincicome, Laura Diaz
68 - Lee Mi-Rim (KOR), Amy Yang (KOR), Jaye Marie Green, Brianna Do, a-Linnea Strom (SWE), Silvia Cavalleri (ITA), Nontaya Srisawang (THA), Prima Thammaraks (THA), Lee Min (TPE), Nelly Korda, Jacqui Concolino, Tiffany Joh, Megan Khang, Kim Hyo-Joo (KOR), Candie Kung (TPE), Kang Hae-Ji (KOR)