Salas spent much of the day waiting patiently for Park Sung-hyun to make a rare mistake. When her putts kept rolling in Friday, she was virtually unbeatable.
Sung Hyun Park, of South Korea, holds the trophy after winning the Indy Women in Tech Championship golf tournament.
"I have been so confident the whole year", Salas said. "My putting overall was what really helped".
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.
Danielle Kang and Nasa Hataoka sit two back of Park and Salas at 11-under par.
"I'm going to do really well", said Park.More news: Governor issues emergency proclamation as Lane churns toward Hawaii
"I had to change my mentality a little bit".
Park has two majors and four overall LPGA Tour victories the last two years, winning the U.S. Women's Open and CP Women's Open last year and the Volunteers of America LPGA Texas Classic and KPMG Women's PGA Championship this season.
Nothing rattled Park on a sticky, overcast day.
"I dropped my score on the last four holes so I have to be careful", said Hataoka, who has made 20 birdies over the last three days. Eight players recorded all four rounds in the 60s, with seven of those players finishing in the top 12. She entered the week in Indianapolis ranked No. 4 in the world and wit her victory on Sunday is projected to overtake Ariya Jutanugarn at the top of the rankings.
Salas took a different tack one day after tying Mike McCullough's course-record 62.
After finishing, Park was whisked away to the Indianapolis Motor Speedway's finish line, where she celebrated by kissing the bricks and taking the traditional sip of milk - though she declined to take the milk bath as the event's inaugural victor, Lexi Thompson, did past year. On day one, Yin had an opening round for the record books with eight birdies in nine holes.More news: Iran urges EU to speed up efforts to save nuclear deal
Park had missed her own birdie attempt at the 18th in regulation, but in the playoff, she drained a six-foot downhill putt to beat Salas.
"Mentally you have to be strong", Yin said after her low round Thursday. "That was my goal this week". And just I stuck with positives, I stuck with my game plan.
Angel Yin is one of those who will have to finish her second round Saturday morning. Only a par on No. 6 prevented her from becoming the sixth LPGA player to shoot 27 on nine holes.
And the course could change dramatically as it dries out.
Park promises to be ready for whatever weather arrives. "So I'm just going to go out and play as if I'm behind". "I feel really good about my game, especially my short game, since my practice".More news: Ariana Grande Performs ‘God Is a Woman’ at VMAs