Olympic tennis semifinals preview

Juan Martin del Potro shocked Roger Federer to pull off the upset at the 2009 U.S. Open. (AP) To the extent grass court tennis played in a best-of-three set

Juan Martin del Potro shocked Roger Federer to pull off the upset at the 2009 U.S. Open. (AP)

To the extent grass court tennis played in a best-of-three set format can be predictable, so it has gone at the All England Lawn Tennis Club in southwest London. Through four rounds, the favorites have eased through, with three of the top five men and women through to the semifinals, and a pair of accomplished spoilers hoping to cause an upset.

Here's how the semifinals shape up:

Men's

Roger Federer (1) [SUI] vs. Juan Martin Del Potro (9) [ARG] (First match, Centre Court): Few can forget the Argentine's break-out party in 2009, when he came back from two sets to one down to Federer in the U.S. Open final to capture his first and only Slam title. At the time it felt like a new star had arrived, one who had the firepower to challenge guys like Federer and Rafael Nadal on the biggest stages, but a series of injuries (most notably the wrist) derailed his progress. Slowly but surely, Del Potro has worked himself back into the mix, but he still hasn't been able to find that 2009 form. For a guy who had eight top five wins in 2009 alone, Del Potro has notched just one this year (def. Tsonga, Dubai).

Though he's still dangerous, possessing a cannon-like forehand that can leave a stadium gasping for air, the Argentine no longer strikes fear in his opponents. Asked about the match-up Federer summed it up perfectly. "I have his number this year," referring to his 5-0 record in 2012, including a come from behind win after being down two sets to none at Roland Garros two months ago. After a slight wobble in his opening match against Colombian Alejandro Falla, Federer hasn't dropped a set since and his focused, surgical win over Isner in the quarterfinals merely emphasized how much he believes in his game right now. Ousted from the doubles competition on Wednesday, Federer's chances of a gold medal rest solely in singles. He was my pre-tournament pick and nothing's happened to change that.

Novak Djokovic (2) [SRB]vs. Andy Murray (4) [GBR] (Third match, Centre Court): This is the popcorn match between two men who carry the weight of their respective countries on their shoulders. For Murray, never has he received such vocal, ardent support than during this Olympics -- that's right, Centre Court was never this loud even when he was in the final of Wimbledon last month. As Murray famously told the British public through his post-Wimbeldon loss tears, the support means the world to him and has consistently propelled him to his best tennis.

He'll have loads of it against Djokovic, a man who cherishes the opportunity to play for his country in a way that few others do. Novak is the face of Serbia, an ambassador to the world for a country still grappling with problems, treated as something beyond royalty back home in Belgrade. And the thing is, he embraces the pressure incumbent to the role. Win a gold medal here, Serbia might as well put his smiling face on the dinars. Djokovic has looked lethal through most of the tournament and the most improved aspect of his game today compared to a few weeks ago is his serve. You can't expect to win matches on grass without a strong serve and Djokovic has used his with ruthless precision.

Women's

Victoria Azarenka (1) [BLR] vs. Serena Williams (4) [USA] (Second match, Centre Court): The Wimbledon champion has been the most dominant player, male or female, all week. Riding a 15-match win-streak heading into the semifinals, she hasn't lost more than five games in any of her matches, coming off a particularly impressive 6-0, 6-3 shellacking of former No. 1 Caroline Wozniacki. Put simply: Serena has cruised, but that's not always a good thing. Just look at her major performances since coming back from illness and injury last year. She cruised into the final of the U.S. Open without dropping a set, only to be stunned by Sam Stosur. She didn't drop more than five games in a match going into the quarterfinals at the Australian Open and lost in straight sets to Ekaterina Makarova. Riding a 17-match clay win-streak into the French Open, she lost in the first round to Virginie Razzano. Yet she arrives at Wimbledon in June with her confidence completely shattered, has to fight through back-to-back three set matches in the third and fourth round to move on, and then again, pushed to a third set in the final by Agnieszka Radwanska, finds a way to capture her first Slam title in two years.

So yes, Serena Williams is downright dominant right now and on paper she should book her spot into the gold medal match. But let's not forget that in their Wimbledon semifinal match, Serena had to fire down a record-setting 24 aces to beat Azarenka 6-3, 7-6. The Belorussian hasn't won a title since March, but she's still one of the most solid hitters off the ground who can consistently get the ball deep on Serena, forcing her to hit off-balance and falling backwards. Serena might be able to get past 90 percent of her opponents playing her B game, but not Azarenka.

Maria Sharapova (3) [RUS] vs. Maria Kirilenko (15) [RUS] (Second match, Court 1)