Roger Federer's fourth-round loss
With only one ATP World Tour title to his name this year, Roger Federer was understandably overshadowed by the likes of Novak Djokovic, Rafael Nadal and Andy Murray when it came to naming favorites to win this year's US Open. But nobody would have predicted his shocking straight-sets loss to No. 19 seed Tommy Robredo of Spain in the fourth round - a loss that marked the first time Federer lost here before the quarterfinals since 2003. The veteran Robredo played one of the finest matches of his career, but the five-time US Open champion had owned the Spaniard in all 10 of their previous career meetings. The Swiss champion seemed shell-shocked in his post-match press conference, leaving tennis fans curious as to how he will respond and regroup during the fall season.
Stanislas Wawrinka's semifinal run
As his four wins over Top 10 players in 2013 alone would attest, Stanislas Wawrinka's talent has been undeniable. But while he's racked up plenty of impressive results over his career, the Swiss player has struggled to put it all together at the majors and maxed out at three quarterfinal appearances (including one at the 2010 US Open). In Flushing Meadows, however, the No. 9 seed finally achieved his breakthrough after well over a decade on tour, reaching his maiden Grand Slam semifinal. His fourth-round win from a set down over No. 5 seed Tomas Berdych of Czech Republic was impressive enough, but it was his straight-sets dismantling over No. 3 seed and defending champion Andy Murray of Great Britain that truly made tennis fans sit up and take notice. Although he lost an arduous five-set match to No. 1 seed Novak Djokovic of Serbia, several of the rallies in that match are destined for the tournament highlight reel. And better yet, his fortnight in New York served notice that Wawrinka could be a force to contend with among the game's elite for the next few years.
Flavia Pennetta's maiden Slam semi
Flavia Pennetta is a former Top 10 player, but injury and some inconsistent results had driven her ranking down into the 80s entering this year's event. The Italian lost in the second round of qualifying at a WTA Tournament in New Haven the week before the Open and only made it into the main draw of this year's tournament due to player withdrawals at the last minute. She took full advantage of the opportunity, however, cruising into her first Grand Slam semifinal without losing a set. After dismantling No. 4 seed and fellow Italian Sara Errani in the second round, she took out 2004 US Open champion and No. 27 seed Svetlana Kuznetsova in the third round before cruising past No. 10 seed and countrywoman Roberta Vinci into the quarterfinals. Although she lost to No. 2 seed Victoria Azarenka of Belarus in the semifinals, Pennetta's ranking will rise from No. 83 to No. 31 after this tournament. With no points to defend until February, it will be interesting to see how far she can climb in the next six months.
Victoria Duval's upset over Samantha Stosur
Victoria Duval was ranked No. 296 in the world and needed a wild card just to get into the qualifying draw, so tennis fans could be forgiven for not expecting much from the young American at this year's event. The bubbly 17-year-old endeared herself to fans last year with a first-round loss to three-time US Open champion Kim Clijsters under the lights on Arthur Ashe Stadium, but her fan base rose exponentially this year. After impressively coming through three rounds of qualifying without losing a set, she pulled off arguably the biggest upset of the tournament in defeating No. 11 seed and 2011 US Open champion Samantha Stosur of Australia. Showing no signs of being overwhelmed by the occasion, she took advantage of some loose play by the Aussie and the rowdy Louis Armstrong Stadium crowd, firing off a forehand winner on match point and jubilantly celebrating. Although she lost in the next round to eventual quarterfinalist Daniela Hantuchova of Slovakia, she passed her first media storm afterward with flying colors, including an appearance on "The Tonight Show with Jay Leno." Fans of Duval can also now follow her on her recently activated Twitter page, which has already received tweets of encouragement from rappers Snoop Dogg and Lil Wayne.
Bryan brothers, Williams sisters fall in doubles
After winning the "Bryan Slam" by capturing four majors in a row with their Wimbledon men's doubles win this year, Bob and Mike Bryan came to New York pursuing the first calendar-year Grand Slam since Ken McGregor and Frank Sedgman in 1951. Their doubles match received plenty of press and TV coverage, with their final three matches all being played inside Arthur Ashe Stadium, but they fell in a heartbreaking semifinal to No. 4 seeds Leander Paes of India and Radek Stepanek of Czech Republic. And while Venus and Serena Williams had only played one other event together this year, they are almost always considered to be the favorites to win when they enter the doubles draw. No. 5 seeds Andrea Hlavackova and Lucie Hradecka of Czech Republic had something to say about this, though, striking their ground strokes with authority and taking advantage of loose net play from the Williams sisters to record a dominant 6-4, 6-2 win in the semifinals.