Serena Williams, who needs just three more wins to secure her twelfth grand slam title. Photo via d.yimg.com

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Six matches for Tuesday, as the stakes get higher and higher for not only the players but also for my predicting reputation...

Women's Bottom Half Quarterfinals

Flavia Pennetta ITA (10) vs. Serena Williams USA (2) -- Pennetta manages to give Serena's sister Venus a lot of trouble when they play, having beaten Venus three times.  She's only faced the younger Williams once, in a losing effort last year in Miami.  Serena has looked untouchable throughout this tournament, and while Pennetta might be able to drag some pointsout longer than Serena might like, there's no way she loses under the lights in the quarterfinals of her home slam.  Prediction: Williams in 2.

Li Na CHN(18) vs. Kim Clijsters BEL -- Li is a dangerous opponent with nothing to lose, but Clijsters is playing some truly inspired tennis in this tournament, and certainly has her eyes set on a semifinal vs. Serena.  I think Li may be able to sneak out a set in this one, but Clijsters will be better in the business end of the match.  Prediction: Clijsters in 3.

Men's Bottom Half Round of 16:  

Gael Monfils FRA (13) vs. Rafael Nadal ESP (3) -- If you like your tennis energetic but defensive-minded, this is THE dream match up for you.  Nadal and Monfils will work up big sweats in their respective sleeveless Nike shirts through some rallies that are likely to take longer than the average Karlovic serve game.  This one could go extremely late into the night if Monfils thinks he has a chance.  If he gets demoralized early, it could be a quick win for Nadal in straight sets (though each set would probably take an hour).  Nadal looked banged up against Almagro, while Monfils has been winning with some ease.  I'm going with the upset in this one, but if Monfils doesn't show up playing to win I could look real stupid.  Prediction: Monfils in 4.

Marin Cilic CRO (16) vs. Andy Murray GBR (2) -- This is a great match-up for Murray, who should be able to neutralize the one-dimensional Cilic's game effectively and win this one without too much trouble.  Cilic's power could also serve as a useful warm up for a likely quarterfinal against del Potro.  Prediction: Murray in 3.

Juan Martin del Potro ARG (6) vs. Juan Carlos Ferrero ESP (24) -- This Juan-on-Juan match should be a fun one.  del Potro has strangely played all four of his matches now on Armstrong, so he should feel quite comfortable out there on the second-biggest stage.  It's strange they haven't managed to rotate him into Ashe at any point, a disadvantage he could rightly complain about if he faces four-time Ashe player Murray in the quarterfinal.  Court assignment aside, del Potro should be able to hit through Ferrero's speed and counter-punching, though not without some struggle. Prediction: del Potro in 4.

Jo-Wilfried Tsonga FRA (7) vs. Fernando Gonzalez CHI (11) --Two forehands this big colliding is sure to leave a few dents in the Armstrong court.  The two former Australian Open finalists both play well on this fast surface, and should both be able to give the other a lot of trouble on offense alone.  But the edge in defense should go to Tsonga, and that's where I believe this match will finally be won.  Prediction: Tsonga in 5.