Wilson had been her coach since Ko was shorter than the golf clubs she now wields. They have had a close and successful sporting relationship.
There is no doubt that Ko could have taken Wilson on full time. But while this must ultimately be a Ko decision, it has IMG's fingerprints all over it. Her management company will have looked at Wilson, assessed the influence he has over the 16-year-old and decided that leverage will be all the more easily achieved if theirs is an uncontested voice in her ear.
But big changes can bring, well, big changes. Ask Michelle Wie.
A one-time idol of Ko's, Wie was supposed to be the female Tiger Woods when she burst on the scene at 10 years old - the youngest player to qualify for a USGA amateur championship. She became the youngest winner of the US Women's Amateur Public Links tournament and the youngest to qualify for a LPGA Tour event.
She turned professional just before her 16th birthday in 2005 in a flood of publicity and expectation that saw her heralded as the new face of women's golf. Sponsors Nike and the LPGA pushed her relentlessly, almost shamelessly. There is an argument to say they took a nascent, previously unseen talent - and stunted it.
She even turned up in men's tournaments, in another barrage of publicity, though she missed the cut 12 of the 13 times she played with the men. That decision to try to foot it with the blokes cost Wie.
She was criticised by many for being a showboater and a glory-seeker when she should have been doing the hard yards on the women's tour.
At her first professional tournament, she was disqualified for an incorrect scorecard and then missed the cut at her second event.
Now, seven years later, Wie has still won only two LPGA tournaments.
Her form fell away sharply and she decided to go to university, graduating from Stanford with a communications degree before heading back to full-time professional golf.
Wie started by missing six cuts in a row; most judges said her problems were mental.
She recovered but this year was ranked only 61st in the world and her best showing in the five women's majors was a tie for 28th; her worst was a withdrawal from the US Open after hitting an 80 in the first round.
She won only US$355,000 last year (most of us would be happy with that but, in pro golfing terms, it's a couple of 20c coins and a bent washer) and US$2.9m in her career.
Wie hits the ball huge distances with a beautiful swing but the mental toughness dimension was underscored by women's golfing great Annika Sorenstam, who said in an interview in 2010 that Wie "has one of the best swings in the game" before pointing out that winning required more than just a pretty motion.
"I stand by them [earlier comments questioning Wie's psychological make-up].
"I still feel so.
"You would think that being on the scene for many years now that she would have [succeeded] a lot more," Sorenstam said.
"It just goes to show that it's a lot more than a golf swing that matters and the mental aspect is a really important part of the game."
There are two points to make here: Wie and Ko seem to be different characters, even though their careers have taken startlingly similar paths thus far.
Wie is tall (1.85m), lithe, with a model's good looks. Ko is tiny, bespectacled and seemingly well stocked with reservoirs of common sense. Like Wie, she has a technically superb swing. She may outstrip her former idol when it comes to mental strength and the ability to win.
Like Wie, Ko wants to attend Stanford. Like Wie, she will be ineligible to play college golf because she is a professional.
Woods also attended Stanford but shelved his academic career after only two years - instead bursting onto the golf scene in one of the sport's most dominant phases ever.
In that sense, Ko's timing going pro seems sound - this is her time; she is dominating and can cash in and become a legend.
But, so far, the indicators seem to be that pursuing a university and pro golfing career don't mix terribly well.
Another potential stumbling block for Ko is new coach Sean Hogan.
The impulse to tinker, to put their mark on a player's career, is almost irresistible for many coaches. It doesn't always work.
It has to be said, at the end of all this, that, financially, Wie's career has not been a failure.
She is said to have earned US$10 million a year from deals with Nike and Sony when she went professional.
She also is reported to have earned US$700,000 in appearance fees at one of those men's tournaments in Korea.
Earning great money and being a great are different things. Ko has the chance to do both.
What we will see in 2014 is whether she has the mental strength to deal with such massive changes in her life.
She has had Wilson and her parents as bulwarks against the pressures of golfing life; the comfort of the familiar. Now one of those comfy cushions has been removed and she is bumping up against the hard realities of pro golf; it is grow-up-fast time. She has time on her side and, seemingly, the down-to-earth ability to cope. Her residence in the US will cause some paranoia in New Zealand ranks that she may defect to play under a Korean or even a US flag, particularly if IMG feels she has more revenue opportunities by doing so.
But such moves are not always successful.
Remember Cecilia Cho - the young Korean Kiwi who beat Ko in the 2009 New Zealand amateur championships and was also ranked the world's No.1 amateur?
She then got right up NZ Golf noses by reverting to Korean citizenship after she turned pro.
Cho is now on the lucrative Korean LPGA tour. Her earnings will be right up there. Her world ranking is 324.
