Defending champion Lydia Ko shot a five-under 67 to seize the opening-round lead at the LPGA Tour’s Swinging Skirts Classic tournament on Thursday.

The world No.1 from New Zealand looked confident and comfortable in the first round much as she did last year when she picked up her first professional win at this event.

“I read most of (the greens) really well,” Ko said. “I tried to be confident with the reads I had. It’s tough here so you can’t really be overly aggressive.”

Ko, who turns 18 on Friday, has won six times on the LPGA Tour. Her first win came at the 2012 Canadian Open as an amateur.

Juli Inkster, 54, posted a four-under 68 and she is tied for second, one stroke behind Ko at Lake Merced Golf Club. The 2015 Solheim Cup captain is joined there by Jang Ha-Na of South Korea and Thailand’s P.K. Kongkraphan.

Minjee Lee was the leading Australian on 71, one stroke clear of Sarah-Jane Smith.

Karrie Webb opened with a 74, Sarah Kemp and Katherine Kirk both carded 76s and Su Oh signed for a 77.

Inkster hasn’t won an LPGA Tour event since capturing her 31st career victory in 2006.

“Age matters in a lot of things, as far as how your body feels, how far you hit the ball and how much time you can put into it – but you can still go out there and compete at 54,” Inkster said.