March 2014 has been an impressive month for Japanese tennis.  Not known as a superpower of the sport, Japan produced a Masters 1000 semifinalist in Kei Nishikori, who upset two top-five opponents in David Ferrer and Roger Federer at the Sony Open.  The island nation also is preparing to host a World Group quarterfinal next weekend.  And, on Monday, Kimiko Date-Krumm knocked off the top seed at the small International tournament in Monterrey. 

Returning to the WTA Tour in 2009 at the age of 38, Date-Krumm lost little time in proving age just a number.  The former world No. 4 scored several notable wins over the next two years, including Dinara Safina at Roland Garros, Maria Sharapova at her home event in Tokyo, and Li Na in Bali.  Between 2011 and 2013, however, Date-Krumm's spirited comeback had started to sag.  She compiled losing records in each of those seasons and even lost 11 straight matches in 2012.  

But the Cinderella story of women's tennis has hinted at a mild resurgence over the last several months.  Now 43, Date-Krumm arrived in Monterrey this week with some solid results behind her.  She had taken a set from Dominika Cibulkova mere weeks before the Slovak reached the Australian Open final, and she had outlasted fiery young Spaniard Garbine Muguruza in Thailand.  That said, a first-round meeting with Flavia Pennetta in Monterrey cast Date-Krumm in the role of a clear underdog.

Earlier this month, Pennetta had won the most significant title of her career at the BNP Paribas Open in Indian Wells.  The 32-year-old Italian had stunned two top-five women in Li Na and Agnieszka Radwanska to claim that desert prize.  Reaching world No. 12 as a result, Pennetta also had shone at the last two hard-court majors.  A semifinal appearance at the US Open last fall preceded a quarterfinal run at this year's Australian Open.

On the other hand, Pennetta has struggled to translate her success from one week to the next and from majors to lesser events.  She lost three straight matches shortly after her US Open semifinal, and she fell in the first round of Doha to doubles specialist Hsieh Su-Wei after the Australian Open.  Her form in the first round of Monterrey, like her third-round loss in Miami, continued these struggles to build on success.

The statistics showed a match more lost by Pennetta than won by Date-Krumm.  The Italian struck eight double faults in two sets while serving at a meager 45%, not an acceptable rate for a relatively low-risk server.  Still, Date-Krumm pounced on her opportunities with alacrity.  She converted five of her six break-point opportunities while protecting her vulnerable second serve with a strong first-serve percentage.

The 7-5 6-2 triumph moved Date-Krumm into another intriguing clash, this time against 2012 Monterrey champion Timea Babos.  This young Hungarian will project more power than Pennetta but will find her opponent's distinctive style a test of her patience and fortitude.  In their only previous meeting, Babos rallied from dropping a befuddled first set to edge Date-Krumm by the narrowest of margins.  Another contrast of styles in the rematch should offer compelling tennis.

Pennetta's loss leaves two former No. 1s as virtual co-favorites for the Monterrey title.  In the other half of the draw, Ana Ivanovic and Caroline Wozniacki will play their opening matches on Tuesday.  Both face dangerous opponents in Urszula Radwanska and Coco Vandeweghe, respectively, so the Monterrey draw could descend into chaos sooner rather than later.