In February, she named Gary Gilchrist her new coach. She tweaked her pre-swing routine, moving her hand up the club on her second practice stroke and letting momentum carry her a few steps forward. Thursday, she used a new putter that, outside of a few inches here and there, produced the desired results.
"I think I just tried to trust my stroke. That's all you can do, just commit to the line you have and put a good stroke on it," Ko said of her strong putting Thursday. "The greens are firm and fast like they normally are at the U.S. Women's Open, so I was trying to just be positive and just be patient.
"I think those two words are really important for me, just don't get too caught up in the bogeys or the missed shot that I had or the one putt I missed."
After the Women's PGA Championship at Olympia Fields Country Club in Illinois, it would have been easy for Ko to pore over her missteps. She went into the weekend at 4 under, three strokes off the lead, and then stumbled through the final two days. A 5-over third round included five bogeys. A 4-over fourth round included five more. She finished tied for 59th place, 18 strokes behind champion Danielle Kang.
Instead of overanalyzing and making impulsive changes to her swing, Ko took a few days off. She had a few friends over to celebrate the Fourth of July. She and Gilchrist combed through the four rounds and pulled out positive takeaways. When things got quiet and golf could have crept into her mind, she found a clear table and indulged a new pastime.
"I found a new hobby," Ko said Tuesday through a grin. "I build, like, Lego houses. It says for 6- to 12-year-olds. It took my mind off of golf."
When she started training again, Ko played a variety of courses to prepare her for the unpredictability at Bedminster.
In the lead-up to the tournament, players discussed massive greens and tricky roughs as two challenging variables. Ko mostly avoided them on Thursday with strong approach shots, even when her drives weren't as accurate as she would have liked. Starting her round on the back nine, she birdied every other hole from No. 10 to 15, then sunk back-to-back birdies on the 18th and first holes. She needed just one putt to finish the 18th, first and second holes, and soon lined up a 12-foot birdie putt at the par-3 fourth.
As she circled the green and sized up the shot, a swelling crowd settled into an anticipating quiet.
"Her putting has been amazing," whispered an older man as he hid from the beating sun beneath a nearby tree.
"Shh," a woman next to him shot back. "Don't jinx her now."
With that, Ko stepped up to the ball, slowly moved her right hand onto her putter and tapped it to the right of the hole. As it hooked back, fans yelled "Go! Go!" and "Get in!" and Ko started forming her guide hand into a celebratory first.
And then the ball disappeared into the hole and out of sight, safe from any frustration and the glares it tends to bring.
"I haven't had much of a good start at the U.S. Women's Open," Ko said after her round.
"But, you know, this is my sixth Open and no matter how times you're playing I think you always get excited and a little bit of the butterflies on the first tee, and I think this is the biggest major championship. We all want to peak at this time of the year so I'm happy with the way I started."