DANVILLE, Calif. — Lorena Ochoa is running out of tournaments in a startlingly average season for a player who won 21 times in the previous three years.

Since winning the Corona Championship in her native Mexico in late April for her second victory of the year, the top-ranked Ochoa is winless in 10 starts.

South Korea's Jiyai Shin leads the player of the year — and rookie — races and is within striking distance of catching Ochoa in the rankings. Norway's Suzann Pettersen and a handful of other players are also close heading into the CVS/pharmacy LPGA Challenge, set to start Thursday at Blackhawk Country Club.

"It's not easy so. That's why I need to work harder," Ochoa said Wednesday. "That's why I need to start playing better and do whatever it takes to keep that No. 1 position."

For nearly two years that wasn't much of an issue for the 27-year-old star who replaced Annika Sorenstam at the top of the rankings in April 2007.

But 2009 has been a much different year for Ochoa. She has spent more time in Mexico while playing in fewer tournaments and is in the midst of planning her December wedding to longtime boyfriend Andres Conesa, the CEO of AeroMexico.

On the course, the results have been disappointing.

Ochoa has finished better than 10th only twice in her last 10 tournaments, including a tie for fourth last week in the Samsung World Championships at Torrey Pines. She bottomed out with a 49th-place showing at the Safeway Classic in August.

In majors, Ochoa also has struggled. She was 26th at the U.S. Women's Open and 28th at the Women's British Open.

"My life is changing a little bit and that's just the way it is," said Ochoa, who two weeks ago in Mexico City bristled slightly at criticisms of her game. "Sometimes it's hard to keep that same level and the same rhythm forever. It's been an up and down year for me for different reasons, especially outside the golf course.

"I think it was a good start, what happened the last couple weeks, but I'm trying to get into the winner's circle."

Ochoa has never won the CVS/pharmacy tournament, formerly known as the Longs Drugs Challenge. She was fourth in 2008 and lost a playoff to Pettersen in 2007.

"Compared to previous years I think this course is going to change a little bit probably with lower scores," said Ochoa, citing the softer greens at Blackhawk. "The par 5s are not as easy in terms of reaching because they are playing longer but I just like it. I've been close a few times so hopefully this is my year."

The 21-year-old Shin has been comfortable all year. She has a tour-high three wins and five other top-10 finishes.

"She didn't surprise me because we knew how good she was," Ochoa said. "Of course it's not only her. There are a few players that are trying to catch me. It's OK. That's the way it is when you're at the top."

Shin, who remembers following Ochoa as a fan at a tournament in South Korea five years ago, also leads the money list and is trying to become the first player since Nancy Lopez in 1978 to win both player of the year and rookie of the year honors.

Shin, the 2008 British Open champion, was sick earlier this week and wasn't able to play a full round on the Blackhawk Course until Wednesday's pro-am. She's an obvious favorite, along with Pettersen and last year's winner, In-Kyung Kim, but Shin isn't counting Ochoa out.

"She's still a great player," Shin said. "Every week she has a chance for the win. This year's been a little up and down for her but she's a good player."

Other past tournament winners playing in this year's event include Karrie Webb (2006), Christina Kim (2004), Helen Alfredsson (2003), Se Ri Pak (2001) and two-time winner Juli Inkster (1999, 2000). The field also includes 13-year-old Casie Cathrea, a freshman in high school who won a qualifier Monday.