Ko was the best putter on the LPGA Tour last season, ranking first in Putting Average, but has fallen to 87th early on in this campaign. However, things have been improving the last few rounds, and Ko was pleased with her recent results on the greens.
"Putting was better the past few days," said Ko. "I got some longer range putts to go in which I haven't seen that much this season. Those are really bonuses and I was able to combine the whole game well today and I think that was the huge difference between the last couple of days."
Despite her superb round, Ko will need to go even better tomorrow to contend for the title.
Korea's Su-Yeon Jang currently leads the tournament at 17-under after also carding a round of 65. She is three shots clear of Canada's Alena Sharp and American Cristie Kerr, who shot a scorching 10-under 62 for the round of the day.
With her leap up the leaderboard, Ko's grip on the world number one ranking should extend to 77 weeks. There were scenarios which could have seen So Yeon Ryu and Ariya Jutanugarn overtake her with a victory coupled alongside a poor finish for Ko, but both players are now alongside Ko in chasing pack. Ryu is in sixth at 10-under, while Jutanugarn is tied for fifth at 11-under.
Ko says she doesn't pay attention to the rankings, but is aware her position at the top is coming under threat from the in-form chasing pack.
"I haven't been able to play as well as I would have liked. Hopefully now I can straighten things out and play as well as the other girls are doing. There is just so much talent out here," said Ko.
Elsewhere, Danny Lee has fallen off the pace on the PGA Tour at the RBC Heritage event. Lee had a mixed round with five birdies, four bogies and a double bogey to shoot one-over, dropping 20 spots back to a share of 25th at four-under for the tournament.
