Lydia Ko is three shots off the pace after the second round of the latest LPGA Tour event in Michigan.
Rounds of 67 and 68 have Ko at seven-under-par and in a tie for 13th behind the American leader, Lexi Thompson.
Thompson overcame an ailing back to fire a four-under-par 67 and take a one-shot lead after the second round in Grand Rapids.
The defending champion moved to 10-under-par at Blythefield Country Club, a stroke ahead of Canadian Alena Sharp and South Koreans Chun In-gee, Q Baek and Ryu So-yeon.
"I'm not really one to complain about pain because I just fight through it, but yeah, it's hurting," Thompson told reporters.
"I didn't really want to pay attention to how bad it was hurting because then it brings more attention to it and it becomes a mind game."
World number one Ko and number two Brooke Henderson shot matching 68s after the two
teenagers dueled in playoff last week at the Women's PGA Championship where Henderson claimed her first major title.
"Anybody can win," Henderson said. "Anybody can make something happen and it just takes two more really good days and hopefully looking at that trophy on Sunday."
Ko added she was happy with the way she played but said there was room for improvement.
"My ball striking wasn't as good as yesterday so hopefully it can get better progressively on the weekend," she added.