INDIANAPOLIS — Lizette Salas waited patiently for Sung Hyun Park to make a rare mistake Saturday.

When the South Korean mishit her approach shot into the water on the par-4 16th, Salas capitalized quickly.

She rolled in her birdie putt then watched Park make double bogey — a three-shot swing that gave Salas the lead and the momentum heading into the final round of the Indy Women in Tech Championship. Salas closed out her 8-under 64 with a birdie on No. 18 to reach 21 under — two shots ahead of Park and Amy Yang.

"I have been striking the ball really well, and I just had to stay patient," Salas said. "And yeah, putts dropped for sure. I just really felt comfortable."

If she keeps it up one more day, Salas could be celebrating her first tour win since the 2014 Kingsmill Championship and her second overall. With five of the next six players on the leader board ranked in the world's top 30, Salas knows it won't be easy.

The changing weather conditions weather may not help, either. If the forecast for mostly sunny conditions Sunday holds, the soft greens that have kept scores at near record-lows through the first three rounds could suddenly become quicker and less forgiving.

But the 29-year-old Californian seems to have the perfect touch for this course, which weaves around and inside the historic Indianapolis Motor Speedway.

She shot three sub-par rounds and finished tied for fifth last year here. This year, she has three more sub-par rounds including a course record-tying 62 on Thursday and has been atop the leader board each of the first three days.

"I have been so confident the whole year," Salas said. "I have a different mentality, I'm a different player. So I'm just going to go out and play as if I'm behind."

Salas' toughest challenge still could from Park, who spent most of Saturday flirting with a 54-hole scoring record.

She birdied the last four holes on the front side and made back-to-back birdies on Nos. 13 and 14 to reach 21 under with a chance to become the sixth LPGA player to ever finish three rounds at 23 under.

The miscue at No. 16 changed everything.

She never really recovered after dropping two shots, settling for par on the final two holes for a 66 after shooting 68 and 63 the first two days. Yang finished with a 65 after going 68 and 64.

"I was a little weary with right-to-left wind," Park said. "I think a little bit of weariness got to me, but overall, it's OK."

Defending champion Lexi Thompson was five shots back after completing the final nine of the second round in 2 under 34 and shooting 64 in the afternoon.

She made up ground despite being assessed a one-stroke penalty after hitting her tee shot on No. 10 into the sixth fairway and lifting the ball without authority. Rules officials had implemented the preferred lies rule because more than an inch of rain had doused the course.

Thompson still made her par on the hole though it temporarily broke her momentum after making six birdies on the front nine in her first appearance since taking a monthlong break to recover from physical and mental exhaustion.

"Twenty-seven holes, I definitely had a few tired swings toward the end," said Thompson, who finished each of the first two rounds with 68s. "But overall, a lot of positives. I hit it great. I made some really good putts."

Three players — Nasa Hataoka of Japan, Jin Young Ko of South Korea and Mina Harigae — were tied at 15 under. Ko started the third round with a share of the lead but had three bogeys in a round of 70.

Brooke Henderson (68) of Smiths Falls, Ont., was tied for 28th at 9 under. Quebec City's Anne-Catherine Tanguay (70) and Hamilton's Alena Sharp (70) were tied for 42nd at 8 under. Maude-Aimee Leblanc (77) of Sherbrooke, Que., sat at 73rd at 1 over.

Now, all Salas has to do is cash in one more time.

"I've been knocking on the door quite a bit in the last four years, haven't been able to get it done," Salas said. "I've got good players behind me, I've just got to play my game."