Rafael Nadal takes on fellow Spaniard Tommy Robredo in the second night match at Arthur Ashe Stadium. (Chris Trotman/Getty Images)
Here are the storylines to watch on Day 10 of the U.S. Open. ESPN2 begins its coverage at 12 p.m. Click here for the order of play.
Rafael Nadal tries to hold serve: Nadal hasn't dropped serve once in 56 games at the U.S. Open. When he won his first and only U.S. Open title in 2010, he did so behind a markedly improved serve that he was hitting flat with more frequency. That hasn't necessarily been the case this year. Nadal's serve looks about the same speedwise, but he's also been defending it very well from the baseline.
So who will be the first man to break Nadal's serve? It's an all-Spanish battle in the last quarterfinal of the night, as Nadal faces 31-year-old Tommy Robredo (second night match, Arthur Ashe Stadium), who knocked out Roger Federer in straight sets on Monday. Robredo is playing some of the best tennis of his career, but he's 0-6 against Nadal and doesn't have the weaponry to break down Nadal's defense. Robredo played well against Federer, but the Swiss helped him tremendously with a number of errors off routine groundstrokes. Nadal won't be so generous.
Richard Gasquet's recovery skills will be tested: After gutting out a four-hour, 40-minute five-set win over Milos Raonic late Monday night, Gasquet now faces one of the handful of men you never want to play when your'e tired -- No. 4 David Ferrer (second match, Arthur Ashe Stadium). Ferrer, a semifinalist here last year, is 8-1 against Gasquet. Tough ask for the Frenchman, who worked so hard to make his second career Slam quarterfinal.
Five thirty-somethings going for a semifinal berth: It's been a tournament for the veterans, with eight of the 16 men and women in the quarterfinals in their 30s. Five of them are up on Wednesday: Ferrer, Robredo, Daniela Hantuchova, Flavia Pennetta and Roberta Vinci. The last four are trying to make their first U.S. Open semifinal.
Bottom half women's quarterfinals feature three surprise names: Hantuchova will try to take advantage of No. 2 Victoria Azarenka's spotty form to pull off the upset and get back into the semifinals of a Slam for the first time since the 2008 Australian Open (first night match, Arthur Ashe Stadium). Azarenka hasn't played her best, struggling to get past Ana Ivanovic in the fourth round and Alize Cornet in the third round. She's winning ugly and it's a credit to her maturity and experience that she hasn't hit the panic button yet. Their head-to-head is tied 2-2, but Azarenka has won their last two meetings. Hantuchova will need a good serving day to keep Azarenka's strong return game at bay.
In the other women's quarterfinal, Pennetta will attempt to keep her run of form going against her Italian Fed Cup teammate Vinci (first match, Arthur Ashe Stadium). The two have split eight matches but haven't played in more than three years. Pennetta hasn't lost a set through four matches and has knocked out three seeds: No. 5 Sara Errani, No. 27 Svetlana Kuznetsova and No. 21 Simona Halep.