Here are the matches to watch as the men and women all look to grab a spot in the quarterfinals on Monday at the U.S. Open.
Andy Murray (GBR) vs. Milos Raonic (CAN) (second night match, Arthur Ashe Stadium): After struggling in the heat to escape a game Feliciano Lopez 7-6 (5), 7-6 (5), 4-6, 7-6 (4) in the third round, Murray will be pleased to see this highly anticipated match played under the lights at Ashe. First, let's just be happy if this match gets played at all. The two have been scheduled to meet three other times this year, but Raonic gave Murray a walkover in Miami because of an ankle injury and the Olympic champion returned the favor in Toronto when he withdrew citing a knee injury. Raonic won their only career meeting, an impressive straight-set victory on clay in Barcelona in April.
One of the storylines percolating at this U.S. Open is whether this will be the major for Raonic to break through. The 21-year-old has been the hot young prospect for two years now but this is the first time since the 2011 Australian Open that he's advanced past the third round of a Grand Slam tournament, and he's seeking his first quarterfinal appearance at a major. Murray will need to find the focus that has eluded him in stretches through the early rounds. If Murray brings his A-game, this one is a no-brainer. But any dip in form and Raonic's power could have him on a string.
Roger Federer (SUI) vs. Mardy Fish (USA) (third match, Ashe Stadium): The way Federer has been playing over the last few months, it's hard to believe anyone besides Murray or Novak Djokovic can get a sniff at him right now. The five-time U.S. Open champion has rolled through three rounds while playing his distinctive brand of attacking tennis. When these two met less than three weeks ago in Cincinnati, they played an all-out aggressive match that felt like a breath of fresh air in an era full of baseline grinders. Federer won 6-3, 7-6 (4), but if Fish can bring that level of play to this match, it'll be a fun one.
Tsvetana Pironkova (BUL) vs. Ana Ivanovic (SRB) (first match, Ashe Stadium): If Ivanovic doesn't succumb to the pressure of opportunity, she may just finally make her first Grand Slam quarterfinal since winning the French Open in 2008 -- a four-year, 17-tournament drought. In her way is the unseeded Pironkova, who is better known for her grass-court prowess. Pironkova hasn't defeated a top-20 opponent on outdoor hard courts since January 2009 (Patty Schnyder, Hobart). Quick, low-bouncing courts are the surface of choice for her crafty game, which relies heavily on the slice. This match is on Ivanovic's racket, which can be a tough thing if Pironkova succeeds in keeping her off balance and the Serb's powerful game breaks down under the pressure.
Andrea Hlavackova (CZE) vs. Serena Williams (USA) (second match, Ashe Stadium): What Hlavackova's game lacks in nuance it more than makes up for in power. The Czech -- who upset Maria Kirilenko in the third round -- can spend an entire match sending forehands toward the back fence, or she can zone and knock them for winners. That kind of unpredictability is always dangerous, for all parties involved. Williams should get through but watch out if Hlavackova is having one of those days.
Venus Williams/Serena Williams vs. Maria Kirilenko/Nadia Petrova : (first match, Ashe Stadium): How about some props to the USTA for daring to put a women's doubles match first on in the night session? This Olympic semifinal rematch should be good one. I'm interested to see how the crowd reacts. Will it stay in the food court until the men's match starts? Or will Venus and Serena help get doubles the attention it deserves? Courtney's Pet Picks: Nicolas Almagro (ESP) vs. Tomas Berdych (CZE) (first match, Louis Armstrong Stadium; these guys have a history); Angelique Kerber (GER) vs. Sara Errani (ITA) (second match, Armstrong Stadium).