The New Zealander said she had not been fully confident heading into the event at Carlton Woods, the new home of the first women's major of the season.

"To be honest, I struggled the first few times I played around this course, and I was like, I don't know how I'm going to do this," Ko said.

"I think there were more positives than I thought. I wasn't the most confident going into today, so I think there are a lot of good things to take, and hopefully, I'm going to take the not-so-good stuff and polish it up a little bit."

Ko, who started at the 10th, notched her fourth birdie of the day on her last hole, picking up a shot after successive bogeys.

"To finish off with a birdie on the last after bogeying 16 and 17, it's definitely going to make lunch taste a little better," she added.

"Even if you don't hit it the best you can, you can just manage your way around and not try to make it perfect. I know it may not look pretty, but I'm just scrambling my way around."

A win on Sunday would give the two-time major winner the two points she needs to become the youngest eligible player for the LPGA Hall of Fame.