New Zealand's world golf number one Lydia Ko and her coach David Leadbetter have parted ways.
The 19-year-old joined Leadbetter's academy when she turned professional in late 2013.
Despite winning four tournaments this year, including the ANA Inspiration Major in California, and a silver medal at the Rio Olympics, Ko has struggled for form in the latter stages of the year.
Ko has won $10 million and 12 of her 14 LPGA Tour titles under Leadbetter, including two majors.
She was bitterly disappointed with her 41st placing at the final major of the year, the Evian Championship, where she was defending her title.
At the time Leadbetter said her slump was nothing to worry about but said Ko needed to review her schedule.
"Scheduling is one of those things that she's really got to look at because she has really been burning the candle at both ends," he said.
In October Ko split with Australian caddie Jason Hamilton, who she had been with for two years.
In a statement on his website, Leadbetter said, "These things happen in the world of coaching, whether it's Jurgen Klinsmann with the US National Soccer Team or Novak Djokovic who just separated from his coach Boris Becker this week. This turnover is all part of the coaching business.
"Lydia is not only an exceptional player, but also an exceptional person. She is a perfect role model for any young golfer to follow on how to conduct oneself on the golf course, interact with the public, and give back to the game.
"Lydia has been an absolute pleasure to coach... and we wish Lydia all the best for the future."