She has kept her ranking as No1 in the world for the past 75 weeks and had three top 10 finishes this year but her last event missed cut for only the second time in 94 starts, seems to have cast a gloomy feel about her chances this weekend in California.
When a keen golfing couple asked me what had gone wrong with her game, my response about Ko still being No1 in the world didn't earn much cut through.
They were concerned her lack of wins was a pointer towards tougher times.
Perhaps the reduced television coverage of the LPGA on the other side of the globe left a diminished connection to Ko's exploits.
There's little doubt Ko's fortunes on tour will be tougher as the standard of women's golf continues to rise with the numbers of highly talented and well-coached young athletes bursting out of Asia and the States.
There's the imposing resurgence from Ariya Jutanugarn with pushes from Mirim Lee, Ha Na Jang, In Gee Chun, Amy Yang, Lexi Thomson and recommitted challenges from Inbee Park, Ana Nordqvist, Stacy Lewis, So Yeon Ryu, Brittany Lincicome and Michelle Wie.
After switching to the David Leadbetter coaching concepts a few years ago, Ko has hooked up with coach Gary Gilchrist and made further changes to her swing and changed her clubs as well.
She has gained some more distance off the tee and feels her irons and wedge play has been reliable.
Accuracy will be crucial around a course which is firmer than it has been with the rough a touch more punishing and greens which will ask consistent questions about the most uncertainty in Ko's game.
"I have been struggling with the putter," she said in the run-up to the ANA. She made a number of crucial par saves in last year's tournament to repel every challenge and finish at 12 under par but this season her putting has been variable.
Golf at the highest level is a tough gig and success is a very singular pursuit.
Ko works extraordinarily hard at her game on and off the course but she is not a golf geek who dispenses with everything else in her life.
She's studying for a degree, loves to broaden her knowledge through travel and has suggested by 30 her career will be done and dusted.
She's also No1 in the world, the defending champion and someone the rest of the field will have to beat if those putts start falling.