New Zealand's World Golf Hall of Fame inductee Bob Charles said the 19-year-old prodigy needed to stop looking "outside her environment" and seek advice from her former coach, Guy Wilson.
"Please, please don't go out looking for another David Leadbetter or whatever, just go back to Guy," Charles told Fairfax Media.
"Just have casual conversations with him and I think she would be a lot happier. But forget about looking for people outside of her environment."
New Zealand's Ko was guided by Wilson for 11 years before she moved on in 2013 and joined the academy of Leadbetter, the renowned US-based British coach.
Leadbetter announced they were parting company in a statement on his website, Ko's latest big change after she sacked her long-term caddie in October.
"It's been particularly difficult the last few months," Leadbetter told Radio Sport in New Zealand.
"Her father has got a little more involved, trying to throw some swing technique at her... Changing her caddy with less than three weeks (left in the season) was a crazy decision."
Under Wilson, Ko was the world's top-ranked amateur for 130 weeks, won two LPGA tour events and never missed a cut in 25 professional tournaments.
After joining Leadbetter, she won 12 titles including two majors on the LPGA tour and an Olympic silver medal.
She won three times early this year but has faltered in the latter part of the season, with just one top-five finish in her last nine starts.
Ko blossomed early in her time with Leadbetter but began to strike problems following advice to change her swing, a move Charles was totally opposed to.
"She's enjoyed a lot of success without making a lot of swing changes and I don't see why she needs to make any major adjustments to her swing," he said.
"I'm a great believer in self-reliance and that you don't rely on a coach. They can offer advice and perhaps give you a few swing thoughts but to stand there with you week after week, I think that tends to confuse the mind.
"The less swing thoughts you have in hitting a golf ball the better."
Charles, the first left-hander to win a major, said Ko should look no further than Wilson if she feels she needs advice.
"Lydia gives the impression outwardly of not taking the game too seriously," he said.
"She's relaxed on the golf course, unlike Tiger Woods who looks the exact opposite. She looks pretty relaxed and to me that's the best way to play the game."