Coming off a playoff victory last week, World No. 1 Yani Tseng of Taiwan bids for her ninth triumph of the year starting Thursday at the $1.3 million Navistar LPGA Classic. Tseng hopes to add the $195,000 top prize to a tour-best $2.1 million in 2011 earnings. Her rivals include World No. 2 Suzann Pettersen of Norway, World No. 3 Cristie Kerr, an American, and World No. 4 Na Yeon Choi of South Korea. "I feel pretty good. I've got lots of confidence right now," Tseng said. "My goal this year was to be No. 1 and I did it. "Now I just keep achieving my goals, like hitting the driving straighter and bunker shots save more and getting my putting average lower. I just keep doing it this year and it seems to work out pretty well." Tseng has been atop the rankings since February 14 but has found staying on top for 30 weeks tougher than the achievement of climbing to the top. "It's difficult to defend the No. 1 position because when you have a goal of getting there, you just keep trying to achieve it," Tseng said. "I'm No. 1, but I feel like I still have a long way to go. I still have so many things I need to learn, I need to achieve and I need to work on. I'm only 22." Tseng became the youngest golfer, man or woman, with five major titles when she won last month's Women's British Open. Her other LPGA titles this year include last week's Northwest Arkansas Championship, the 10th LPGA victory of her career, plus the Honda LPGA Thailand, LPGA State Farm Classic and Wegmans LPGA Championship. Tseng also won the Women's Australian Open and the ANZ Ladies Masters last February. Australia's Katherine Hull will try to defend her title this week. She claimed her second career crown last year by edging American Brittany Lincicome by a stroke. Hull's other LPGA victory came in the 2008 Canadian Women's Open. This year, Hull's only top-10 effort was a share of sixth at Mobile, another Alabama event where she feels a touch of Australia. "It actually reminds me of home, like the laid-back kind of personality of people," Hull said. "It's nice to be here. I love this golf course obviously and happy to be back and defending. "Swing-wise it feels pretty good. Golf for me right now is all mental. It's such a game of confidence and I'm just going to try and get that back." This is the last before LPGA players leave America for events in South Korea, Malaysia, Taiwan, Japan and Mexico ahead of the season-ending LPGA Titleholders tournament in Orlando, Florida. An event scheduled in China in two weeks has been cancelled.