Lydia Ko of New Zealand shot a 6-under 66 to open up a five-stroke lead at the CME Group Tour Championship on Friday in Naples, Fla.

Ko led after the first round and once again posted the lowest round Friday, shooting six birdies and no bogeys at Tiburon Golf Club to get to 13-under 131 through two rounds. Her closest competitor is South Korea's Hyo Joo Kim, whose 69 took her to 8 under for the event.

A win would give Ko, 25, a trio of awards: the season-long points race that determines the Rolex Player of the Year, the season-long money title and the Vare Trophy for the season's scoring champion.

Ko entered the week as one of four players mathematically eligible for Player of the Year, along with Minjee Lee of Australia, Brooke Henderson of Canada and Atthaya Thitikul of Thailand. Ko led Lee by a point and would claim the award with a tournament victory.

"I already knew going into the day that it could be tricky, but at the same time because I played really solid in the back nine, I knew that if I did make any mistakes, there were birdieable holes coming in," Ko said.

"That's kind of the goal for me this week is not let one hole or one shot faze me. You know, this is the last tournament of the season. It's my ninth year on tour, so I want to finish the season well and also just want to finish it without any regrets."

Ko had few reasons for regret Friday. She made her first two birdies at the par-5 sixth and par-4 seventh holes, then added four more on the back nine, including both par-5s -- Nos. 14 and 17.

"When I am putting well, I just know that, hey, I can make up-and-down from here and there, but at the same time I don't want to put too much stress on it because then that just puts a lot of pressure," Ko said. "Then it's like a revolving circle of pressure over pressure, and that's not where I want to be."

Kim recorded four birdies and one bogey on Friday, with consecutive birdies at the par-3 16th and par-5 17th helping her sneak ahead of the pack into sole possession of second.

"I think I should play well to catch up to Lydia," Kim said. "I think hopefully tomorrow compared to today the greens in regulation percentage will be higher. I think the feel of my putts and my shot is pretty good right now, so I think if I get those birdie opportunities, hopefully I can reduce that gap."

Tied for third at 7 under were Japan's Nasa Hataoka (67 on Friday), Sweden's Anna Nordqvist (69), Nelly Korda (69) and Scotland's Gemma Dryburgh (70).

Korda, the former world No. 1, made four birdies and a bogey going out before parring the entire back nine.

"It doesn't matter what prize money is on the line, what trophy is on the line, I'm going to go and approach every shot 100 percent, and I'm going to stay aggressive and stick to my game plan," Korda said.

In terms of Ko's competition for Player of the Year, Lee shot a 68 on Friday to get to 5 under and a tie for 10th. Thitikul carded a 67 to get to 4 under for the tournament, tied for 18th, and Henderson posted a 74 to drop to 2 under overall, tied for 26th.

--Field Level Media