Lydia Ko is in danger of losing her number one world round if she doesn't bounce back from form at the first major of the LPGA season this weekend.

Ko heads into the ANA Inspiration on Friday as the defending champion but after missing the cut for just the second time in 94 starts last week at the Kia Classic, Thailand's Ariya Jutanugarn is nipping at Ko's heals for the number one ranking.

Ko has been number one in the world for a total of 94 weeks, the third longest amount of time in LPGA history, after first claiming the spot at just 17-years-old.

Her current run at number one has been for 75 straight weeks, after recapturing the top spot on October 26, 2015 from Inbee Park.

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But that run will end if Jutanugarn (8.12 ranking points) wins the ANA Inspiration for the first time and Ko (9.45 ranking points) finishes fifth or worse.

Seven months ago, the average points differential between No. 1 and No. 2 in the world was 6.57 points. This week, the difference is now 1.33 average points.

"I actually can't remember the last time I checked the Rolex Rankings," Ko told media yesterday.

Ko, who has 14 career titles, hasn't won since the Marathon Classic in July last year but she's had three top 10 finishes this year before last week's hiccup.