LEADBETTER SAYS HE didn't want to touch Ko's short game, including her wedges: "You don't mess with a Mona Lisa." But everyone in Ko's camp admired the swing of Hee Young Park, a talented Korean golfer and one of Leadbetter's pupils. Leadbetter agreed that Ko could benefit if she learned to hit the ball higher and farther, and so the experiment began. They began working on an unconventional swing method Leadbetter had been developing for years called the A-Swing. Instead of a traditional backswing in which the club rotates mostly around the player's spine, Leadbetter had Ko taking the club away more vertically, with the shaft pointing almost straight up and down.
"Lydia, as great a player as she is, she's not the greatest athlete," Leadbetter says. "If you look at great athletes, they can make different actions work. The A-Swing in many respects added some athleticism to Lydia's swing. She started getting longer -- her iron play was unbelievable."
Not everyone in the game was a fan. Critics said Leadbetter had ruined her swing and that he was using Ko to sell books that tout his method. "She had a beautiful swing before Leadbetter got his hands on it," tweeted Billy Horschel, a four-time winner on the PGA Tour.
“Lexi [Thompson] was bombing it 40 and 50 yards by her, and Lydia just completely outplayed her.”
Leadbetter helped Faldo remake his swing in the '80s, when he was the No. 1 player in the world, and he was Els' coach for nearly 20 years, when Els won three of his four majors. But he was also given the derisive nickname Lead Poison by tour players and media members after Wie, another teenage prodigy, failed to blossom. Wie, who recently won her first tournament in nearly four years, continues working with Leadbetter.
"Lydia Ko, from the time she was a child, everyone could see where she was headed," says Brandel Chamblee, a former PGA Tour player who now works as an analyst for the Golf Channel. "David Leadbetter completely changed the DNA of her golf swing. Why in the world would you do that? Because you want to put your stamp or signature on the masterpiece that is this kid?"
Regardless of how it looked, it was hard to argue with the initial results. Ko won her first tournament as a professional, the 2014 Swinging Skirts LPGA Classic, just two weeks into working with Leadbetter. She finished in the top 10 as a rookie, winning twice more, and became the youngest player ever to win Rookie of the Year. Time Magazine named her one of the 100 Most Influential People in the World.
Sudden fame was a strange phenomenon for Ko. How's a teenager supposed to react when adults hold up giant cutouts of her face and scream her name? "It's a little weird, to be honest," Ko says. "But when kids come up and say 'You're my role model,' that's my favorite thing. I'd rather have someone say 'You're my role model' than 'You have such a nice swing.'"
But she did have such a nice swing. She quickly became one of the most popular players on tour. In her second year on tour, Ko tied Sorenstam's record by shooting 29 consecutive rounds under par. She won her first major by six strokes, shooting 63 in the final round of The Evian Championship in France while paired with another teenager, Lexi Thompson. "Lexi was bombing it 40 and 50 yards by her, and Lydia just completely outplayed her," Leadbetter says.
Leadbetter says one of his proudest moments working with Ko came the following season, when she won her second major, the 2016 ANA Inspiration. Tied for the lead on the 18th hole, Ko, along with caddie Jason Hamilton, stood in the fairway, sizing up the biggest shot of the tournament, her third into the par 5. She had 82 yards, over the water, to the pin. "You want to aim like half a yard left and let it spin," Hamilton said.
"Going right at it," Ko said.
At times, that's how in control of the golf ball Ko was at age 18, down to the half yard. She put a gentle swing on the ball, posed with her hands high as it reached its apex. Her shot landed short of the flag, hopped twice, then stopped cold, 18 inches behind the hole. After she tapped in for the victory, Ko plucked the ball from the cup and raised her hand to the crowd. She couldn't stop grinning. It looked like a scene that would play out again and again for years to come.
IN GOLF, PLAYERS often peak at a young age and then gradually fade. But in Ko's case, the decline over the past 18 months has been shocking. Looking back, there were warning signs that not everything in her world was perfect. Traditionally, the game's best players might change caddies two or three times in an entire career. Ko changed caddies eight times in her rookie season. It became something of a running joke: Which caddie wants to sign up to be fired next?
Even now, Ko finds that characterization unfair. Several of her caddies, she says, were multiweek tryouts. "I only fired one," Ko says. "That rookie year, I was trying to learn more about myself. What do I prefer? You might think, 'I like a person who doesn't give me anything great on numbers, but I just want him to be super funny.' But then you might realize you do need a little help. It's a learning process."
Leadbetter says if you want to pinpoint a moment when everything started to go sideways, it was the final round of the 2016 U.S. Women's Open at CordeValle Golf Club in California. Ko was playing well, rehearsing Leadbetter's A-Swing takeaway before every shot and leading by a stroke when she came to the ninth hole, a 570-yard par 5 with a creek in front of the green. She tugged her tee shot just a tad, into the left rough, leaving her with a difficult lie and an even harder decision: Go for it or lay up short of the water?
Hamilton, according to Leadbetter, encouraged her to go for it. Cameras picked up his final instructions to Ko before stepping away with the bag: Be aggressive. Ko put a decent swing on the ball, but the rough was so thick, it came out low and plunged into the creek. She ended up making a double bogey and missed a playoff with Brittany Lang and Anna Nordqvist by two shots.
"When she took out a hybrid, I thought, 'That's a crazy decision,'" Leadbetter says. "She had that tournament in the palm of her hand. But she didn't have the confidence to make her own decision. She went by what the caddie said. I thought right then and there: 'If this girl had the license to make her own decisions, she'd be fine. But because she's essentially told what to do by her parents ... she doesn't have the wherewithal to make her own decisions.'"
The involvement of Ko's parents is a recurring theme when you talk with Leadbetter, but Ko insists she controls her own life and is ultimately in charge of her career. Her parents, who have never granted an English-language interview during Ko's career, did not respond to an interview request when contacted by ESPN through Ko's agent, Michael Yim. "Her parents are not the type of people who want to be in the spotlight because they know it's not about them and it's about Lydia," Yim says. The idea that her parents are controlling figures in Ko's life, Yim says, is "totally inaccurate."
After the U.S. Open disappointment, Ko seemed to grow increasingly tired as the year went on, with Leadbetter saying she had put everything she had into the Rio Olympics, where she won a silver medal. Leadbetter had a sports biomechanics specialist on his staff test Ko's leg strength when she pushed off the ground during her swing -- a key aspect of creating swing speed -- and it had deteriorated by 20 percent.
Whatever the physical and emotional cost, Ko views the Olympics as the most important experience of her career. Culturally, so much of her life is Korean, from the food she eats to the language she speaks at home to the shows she watches. But she'd never felt more Kiwi than she did on the final day in Rio, when several of New Zealand's Olympic rugby players and rowers, athletes she barely knew, climbed atop the grandstands and roared with every birdie putt as she went for gold. "The Olympics might be the only reason I'll stick around and play golf after I turn 30," Ko says. "I could see playing in 2032."
Still, through the fall of 2016, Ko's game suffered. Leadbetter and his assistant Sean Hogan tried to talk Ko out of sacking Hamilton, but when she finished tied for 51st place -- her worst finish of the year -- in October at the KEB Hana Bank Championship in South Korea, she fired him in the clubhouse.
Leadbetter found himself on the chopping block that December. Gil, Ko's father, made it clear he didn't like -- aesthetically -- what Leadbetter had done to her swing. Leadbetter sensed the move was coming but says it still stung. He'd lost players before, but never when they were still playing relatively well. Ko, according to someone close to her, was interested in still working with Hogan, the Leadbetter Golf Academy's director of instruction, but wanted to move away from the A-Swing. Leadbetter disagreed. The two sides felt it best to part. Leadbetter insists he has no ax to grind with the Kos; he merely hopes she can someday do what Wie did: break away from her parents enough to take control of her own career.
"They feel like they know her best, know her moods," Leadbetter says. "They're right, they know her. But there is no way she made these changes on her own. There is absolutely no way. Whatever she says, 'I'm making my own decisions now,' that's baloney. They were made for her."
Ko makes it clear, however, that she trusts her family more than anyone. "I respect David and Sean a lot. But in the end, if I'm making any decision, whether I'm going to shop or change caddies or change coaches, I'm always going to talk to my parents about it," Ko says. "No matter what, I'm going to ask them. If it didn't feel right, I wouldn't have done it. I believe in my decision. I have no regrets."
Ko spent 2017 with coach Gary Gilchrist, but shortly before this season began, Ko quietly announced she'd fired Gilchrist and was now working with Ted Oh, a Korean-American golfer best known for battling Woods during his amateur career. She also let go of yet another caddie. She needed a total reboot.
IT MAY TAKE years to sort out whether Leadbetter took a scalpel to the Mona Lisa, leaving it forever damaged, or whether Ko's parents smothered a budding genius.
When Ko missed the cut at the Bank of Hope Founders Cup by four shots in mid-March -- her fourth missed cut in the past 26 tournaments -- LPGA veteran Cristie Kerr (who played two rounds with Ko in the tournament) didn't mince words when asked to assess the former No. 1 player in the world. "Her game is not in good shape," Kerr told reporters. "She seemed a little lost."
One of the things Ko says she likes about psychology is trying to understand why people exhibit certain behaviors. She read one study examining how some companies use psychology to make consumers happier. "It made me think: 'How do you think on the golf course?'" she says. "Why does somebody get mad? Why do they react in certain ways?"
There is a motivational quote from Young-Pyo Lee, a retired Korean soccer player, that Ko keeps returning to when she's feeling low: What you're practicing now, it's not for your next event. It's not for three weeks from now or for later in the season. What you're practicing now is going to be for five years from now. You can't get carried away if something is not working.
To believe in that philosophy is to believe that when she's 25 Ko will be right where she needs to be -- and will have five years left to play transcendent golf before she turns 30 and it's again time to put her trust in the people around her, those who know her best, while mapping out her future.
Kevin Van Valkenburg is a senior writer for ESPN. Follow him on Twitter @KVanValkenburg.