Lydia Ko has accomplished plenty in her short competitive golf career and made the game look easy along the way.

The 18-year-old from New Zealand has collected nine worldwide victories in the last three seasons as an amateur and a professional. She even climbed to No. 1 in the rankings earlier this year — at 17, the youngest man or woman to accomplish the feat.

This season alone, Ko has two wins, two seconds, a third, and three other top-10 finishes.

So, it's no surprise that all that success has lifted Ko among the players to watch when the U.S. Women's Open kicks off Thursday morning at Lancaster Country Club.

She welcomes the pressure and the high expectations.

"I've just got to take it as just another tournament," Ko said. "I'm here. I didn't prepare differently, just because it was a major. At the end of the day I think I've got to think of it as just another event with a great field. And I think that will keep me mentally more stable, no roller coasters."

Ko and the 156-player field can expect plenty of ups and downs over the tree-lined and hilly, 6,400-yard, par-70 William Flynn layout. From elevated tees, the players will be driving into upward slopes, limiting distance, and there is always plenty of thick, sticky rough to contend with at any open. Once on the greens, players will be forced to negotiate slippery, sloping putts.

Ko will also be teeing off against a field that includes 10 previous champions, including last year's winner, Michelle Wie.

Other winners include Na Yeon Choi (2012), Paula Creamer (2010), Laura Davies (1987), Eun-Hee Ji (2009), Cristie Kerr (2007), Birdie Kim (2005), Inbee Park (2008, 2013), So Yeon Ryu (2011) and Karrie Webb (2000, 2001).

Other players to watch include Brittany Lincicome, who won the ANA Inspiration in April in California, and fellow American Stacey Lewis, who finished second to Wie in the Women's Open last year. Standout South Korean rookie Sei Young Kim had her caddie removed from the championship by the United States Golf Association for taking photos of internal notes on the course setup.

Ko's stellar season has been dotted by some trouble. There was a tie for 51st at the ANA Inspiration — but that preceded her second win of the year. In a recent four-week stretch, she went T-41, T-16 and T-27 before missing the cut — her first MC in 54 tries — at the Women's PGA Championship in early June. She rebounded with a tie for sixth in Arkansas, an event that saw her close with a 63.

"It's been a pretty awesome start to the year," Ko said. "I think ANA was really the first tournament where I wasn't top 10. It's been a lot of fun. I didn't play well the last couple of weeks, but it was great to finish with a low score on Sunday in Arkansas."

Sounding like a veteran, Ko has also handled her climb to No.1 in the rankings and her recent tumble from the top like a longtime pro.

"I had that ranking for longer than what I had expected," she said of her January-to-June stay atop the rankings. "Obviously there was pressure coming along with it, but it was fun.

"I think the greatest memory for me was playing in my national Open, New Zealand Open, in front of the home crowd, being the world No. 1, that was a special moment for me. But, obviously, it does motivate me to play better, be a little bit more consistent."