TOKYO, Japan - A day before her 40th birthday, Kimiko Date Krumm gave herself and her home crowd in Tokyo something big to cheer about, upsetting the defending Toray Pan Pacific Open champion, Maria Sharapova.

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In perhaps the most intriguing first round match-up, two former champions of the Premier-level tournament squared off in its first round, Date Krumm winning it all the way back in 1995 and Sharapova taking it in 2005 and last year.

After edging the No.12-seeded Sharapova in the first set, 7-5, Date Krumm, a wildcard into the draw, seemed to lose momentum for a little while, losing three straight games and never getting back on track en route to losing the middle set, 6-3. Sharapova broke again for a 3-2 lead in the third set and had 40-0 to move ahead 4-2 - but that's when the momentum shifted one last time.

Date Krumm won 17 of 21 points from 2-3, 0-40 to win the match, 75 36 63.

"I'm very happy to win this match, especially just a day before my birthday," Date Krumm said. "The crowd really helped me. When I play at home I sometimes feel big pressure, but today I was able to control myself.

"It was a big, big win. I hope tomorrow my body feels okay!"

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Having been unable to defeat a Top 20 player between coming back to tennis in the spring of 2008 and the end of the 2009 season, Date Krumm has now scored five Top 20 wins in 2010, beating Virginie Razzano and Nadia Petrova in Australia, Dinara Safina at Roland Garros, Anastasia Pavlyuchenkova last week in Seoul and now Sharapova, currently ranked No.15 in the world.

Sharapova was playing Date Krumm for the first time: "Kimiko was a new opponent for me, so I had to try and figure her out. She stays low and likes the ball hit hard at her, and then she steps in and changes direction. She did that really well. I had my ups and downs but couldn't take control when I was up.

"It takes a lot to come back and Kimiko is extremely fit."

Next for Date Krumm is Daniela Hantuchova, who won her first round match on Sunday. Date Krumm leads her head-to-head against Hantuchova, 1-0.

"I just played Daniela last year in Korea, so this will be the second time," Date Krumm added. "I'll just try my best and focus on the ball."