U.S. Open Day 9 matches to watch

Rain is expected on Tuesday as the men complete their fourth round and the women kick off their quarterfinals, but the story of the day -- assuming there's play -- is Andy Roddick. As he winds down his career at his final tournament, he is once again the last American man standing, a role that he has played gamely and reliably over the course of his 12-year career. An upset of Juan Martin del Potro would electrify the New York crowd. A loss would mean a big retirement party for Roddick and 23,000 of his closest friends. Either way, it's the must-watch match of the day.

Here's what we hope to be watching on what could be a rain-soaked day.

Juan Martin del Potro (ARG)[7] vs. Andy Roddick (USA)[20] (first night match, Arthur Ashe Stadium):  Could this be the day Roddick bids farewell to tennis? If so, he would be bowing out to precisely the type of new-generation player who represents the sea change Roddick has played through over the past few years. Nowadays the guys are bigger and stronger with the ability to wallop the ball off both wings and pound aces at will.

Sure, I could cite head-to-head records (Del Potro leads 3-1), note that all their matches have been on hard courts and mention that Roddick's sole win over DelPo was more than a year ago in Memphis on indoor hard courts (read: fast). Yet if ever there was a time when numbers felt so trivial, it's now. Since kicking off the Roddick Retirement Tour, the 30-year-old American has defeated Bernard Tomic and Fabio Fognini by playing dynamic, aggressive and -- let's just say it -- fun tennis. The crowd has lapped it up and showered Roddick with adoration. In return, he's pulling pages out of his old coach Jimmy Connors' book as he whoops it up and dials the entertainment value to 11, playing with the self-awareness of a man that knows any match could be his last.

Victoria Azarenka (BLR)[1] vs. Samantha Stosur (AUS)[7] (first match, Ashe Stadium): The women's quarterfinals begin with the defending champion trying to do something she's never done in her career: beat Azarenka. Not only has Stosur failed to knock off Azarenka in six tries but she also hasn't even won a set. The matches have been blowouts. In their last five meetings dating to 2008, the Aussie hasn't won more than five games in any match. This has always been a bad matchup for Stosur, as Azarenka has no difficulty handling Stosur's kick serve and she takes the ball early off the ground, taking away the much-needed time Stosur needs to wind up on her groundstrokes. Look for another rout for Azarenka here. She has been scary good through the first week, dropping a mere 10 games through four matches.

Maria Sharapova (RUS)[3] vs. Marion Bartoli (FRA)[11] (second match, Ashe Stadium): As in the first women's quarterfinal, Sharapova has never lost a set to Bartoli, amassing a 4-0 record dating to 2005. That said, they have not played each other in more than two years and if you saw Bartoli's fourth-round upset of Petra Kvitova, you witnessed a frightening display of precision shot-making.

Meanwhile, if you believe Nadia Petrova's post-match assessment after losing to Sharapova in three sets on Sunday, Sharapova is lucky to be in the quarterfinals at all. Aided by a rain delay after trailing 2-0 in the third set, Sharapova got a pep talk from her coach and her dad and came out firing. Sharapova's response to Petrova's calling her win "lucky": "Great.  I'm the winner, so whatever she wants to call it is fine with me." Lucky or not, Sharapova will need to tighten up her game if Bartoli comes out the way she did against Kvitova.

Stanislas Wawrinka (SUI)[18] vs. Novak Djokovic (SRB)[2] (third match, Ashe Stadium): Djokovic hasn't lost to Wawrinka since 2006 in Vienna when the Serb was just 19. Since then, Djokovic has racked up nine straight wins. Though Wawrinka played exceptionally well in Cincinnati this year in beating David Ferrer, Kei Nishikori and Milos Raonic to make the semifinals (where he lost to that other Swiss tennis player guy), I don't see him getting past Djokovic. The world No. 2 has been been ruthless, dropping a men's tournament-low 14 games through three rounds. (By comparison, Roger Federer has lost 27.) Djokovic has been efficient and minimized his time on court while flying under the radar.

Janko Tipsarevic (SRB)[8] vs. Philipp Kohlschreiber (GER)[19] (second match, Louis Armstrong Stadium): This is probably the most competitive match of the day on paper, even though Kohlschreiber has never beaten Tipsarevic in a completed match -- his one recorded win is via retirement. After having to come back from two sets to none in the first round against French wild card Guillaume Rufin, Tipsarevic has been solid, getting past Brian Baker and Grega Zemlja in straight sets. Kohlschreiber, on the other hand, has put in extra duty, going the full five to upset John Isner in the third round and having to go to a fifth-set tiebreaker to outlast Benoit Paire before that. Can the German recover physically after his 2 a.m. win over Isner? Word is he didn't get to bed until after 5 a.m.

Courtney's Pet Picks

: Richard Gasquet (FRA)[13] vs.David Ferrer (ESP)[4]; Aisam-Ul-Haq Qureshi (PAK)[9] /Jean-Julien Rojer (NED)[9] vs. Christian Harrison (USA) / Ryan Harrison(USA) in men's doubles; Julien Benneteau (FRA) / Nicolas Mahut (FRA) vs. Bob Bryan (USA)[2] / Mike Bryan(USA)[2] in men's doubles; Eugenie Bouchard (CAN)[3] vs. Victoria Duval (USA) in junior girls' singles.