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Wilson said a technical flaw when using the driver undermined the 15-year-old's round, and ultimately her tournament.
A co-leader with Jiyai Shin heading into the final round at Royal Canberra, Ko stumbled over the early holes, enjoyed a brief recovery to challenge again, but then slipped to third behind winner Shin and second-placed Yani Tseng.
Already on her way to her next challenge - the Honda LPGA Thailand, which starts on Thursday - Ko has travelled with advice from Wilson about how she can improve.
"The thing that let her down on the final day was her driver, which she had been so confident with during the week - making 14 or 15 fairways on most of the days - and then when it mattered most it didn't work," Wilson said.
"It was purely a technical thing. I guess nerves might have played a part in that because she couldn't figure it out while playing. She did hit a number of three woods when she would normally use driver; she resorted to playing safe on a few occasions which is the thing to do when your key club isn't going great.
"But on the holes when it mattered most when she was on her fightback, the one that would go left would ruin it."
Ko went left off the first tee, hitting into trees. A duffed second shot left her with a double bogey before she bogeyed the second. With playing partner Shin comfortably making par on both, Ko was quickly three back.
Although she rallied to draw level with Shin on the back nine, for once in her already remarkable career, Ko's consistency wasn't there. Shin went clear before Tseng also overtook her. Ko finished on 14-under, two shots behind Taiwan's Tseng, the world No1, and four shots behind South Korea's Shin.
Wilson said her final-round 76, which was three over par, was one of Ko's worst scores in a tournament "since I can remember".
Asked about her state of mind on Sunday night, Wilson said it was one of extreme disappointment.
"She was pretty peed off, really. She could have won the tournament quite easily and she knows that she's good enough to win week to week.
"The one time that she needed it [a consistent round], it fell to pieces. Even if she had shot even par she could have won, I think. And then to not even come second, to come third; regardless of who the players are she's still pretty peed off."
Shin's extremely slow play earned her an official warning as well as several negative comments on social media from those who believed it a ploy to put Ko off, but Wilson said that wasn't a factor.