Passing shots: No. 2 spot in WTA rankings not suiting Serena so far

One week after Dinara Safina usurped an out-of-form Williams atop the WTA's computer rankings, the 10-time Grand Slam winner -- whose body of work should speak for itself -- made a tacky assertion of her dominance.

"We all know who the real No. 1 is," Williams told reporters in a not-so-thinly-veiled swipe at Safina. "Quite frankly, I'm the best in the world."

The comeuppance was swift. Serena lost her opening match to Patty Schnyder the very next day, while Safina worked through the draw and beat Svetlana Kuznetsova for her first title of 2009.

The plot thickened Monday at the Madrid Open when Williams retired from her first-round match against Francesca Schiavone after dropping the first set, citing a nagging knee injury.

Fans have always admired Serena for her defiance and competitiveness. She's not in the business of making friends nor should she be. But the language of tennis is performance, an area where she's been compromised by her fitness in recent weeks. Monday's retirement marked her fourth straight loss and ensured she'll enter the French Open winless this year on clay, a demanding surface conducive to longer points.

On the flip side of the spat is Safina, the younger sister of two-time major champion Marat Safin, whose career took flight a year ago with her victory over Elena Dementieva in the German Open final. That victory capped a magical week for the young Russian, who'd knocked off top-ranked and top-seeded Justine Henin in the third round (in the last match of her career) and snapped Serena's 17-match winning streak in the quarterfinals.

Safina has flourished since that Berlin breakthrough, finishing second at the French and Australian Opens and bagging Olympic silver in between. A four-time finalist this year, Safina is in the best shape of her life thanks to her work with fitness trainer Dejan Vojnovic. And while Safina's Grand Slam tally (zero) remains light years behind Serena's all-time haul -- the crux of her tormenter's argument -- the rankings simply don't take into account a player's accomplishments from several years ago.

Serena only adds to her pressures by taking swipes at a competitor like Safina, who handled the entire episode with grace and reaped the deserved rewards. If Williams can manage the burden of No. 2 as adroitly as Safina handled her first week at No. 1, Serena will be back atop the rankings in no time.

Serbia's Novak Djokovic spared no expense in bringing the ATP Tour to his home country for the first time, buying a plot of land on the banks of the Danube River, rebuilding a defunct site into a suitable tennis venue and paying out of pocket for the license from the organizers of the former Dutch Open.

Djokovic, whose uncle Goran served as tournament director, didn't let down the hometown crowd in the inaugural Serbia Open last week. The 21-year-old defeated Poland's Lukasz Kubot in straight sets to secure his second title of the year.

But Novak, who slipped to No. 4 in the rankings despite his victory, wasn't the only Djokovic to make waves at the event. His younger brother Marko earned his first match win on the pro tour with a bracket-busting upset in the doubles draw.

The 18-year-old teamed with Darko Madjarovski to stun top seeds Daniel Nestor and Nenad Zimonjic, whose 12-match winning streak had included titles at Barcelona and the Rome Masters.

"This is not a surprise," Marko said after the match, echoing his older brother's famous chutzpah. "The result is real and I hope that we will win the tournament."

One day after the upset, Djokovic and Madjarovski were eliminated by Johan Brunstrom and Jean-Julien Rojer.

One of the world's coolest-looking sports venues makes it debut this week as Madrid plays host to the fifth Masters tournament of the year.

The Mutua Madrileña Madrid Open, which for years was a men's indoor tournament held in October, kicked off its second life as a mixed event Sunday at the spectacular La Caja Magica -- a revolutionary tennis complex that's one of the centerpieces in the city's bid for the 2016 Olympics. (See below for a picture.)

The vision of French architect Dominique Perrault, the Magic Box features three show courts -- each equipped with innovative retractile covers for adverse weather conditions -- in addition to 27 outdoor courts. The largest stadium seats 12,500, with the ancillary courts holding 3,500 and 2,500 fans.

Roger Federer has spent the better part of the past six years ranked either first or second in the world. He may need a good performance this week to stay there.

Federer enters Madrid just 630 rankings points ahead of Andy Murray, who recently became the first British player to climb as high as No. 3. If Murray wins in Spain (where Rafael Nadal is the top seed) and Federer loses before the final, Murray will climb to No. 2 in next week's rankings.

Federer, who has a seven-month title drought, is winless in five tries against Nadal, Djokovic and Murray in 2009.