Here's what Federer needs in Paris

What to watch on Day 4: World No. 1s Victoria Azarenka and Novak Djokovic kick off action on the two main courts on Wednesday, with Roger Federer to follow. And though Serena Williams may have lost, there are plenty of other Americans in action, including Brian Baker, who will make his first center-court appearance as he tries to continue his fairy-tale comeback against Frenchman Gilles Simon. Then Venus Williams will face Agnieszka Radwanska in the highest profile women's match of the second round.

There are plenty of other American women in action. This year's French Open is shaping up as the United States' most successful in years. Former fairy tale Melanie Oudin takes on clay expert Sara Errani; Irina Falconi meets U.S. Open champ Sam Stosur; Vania King goes up against Dominika Cibulkova; and Bethanie Mattek-Sands faces Sloane Stephens in an all-American encounter.

Two men's matches worth catching are Tomas Berdych against net-rushing Frenchman Michael Llodra, and former champ Juan Carlos Ferrero against Marin Cilic.

PARIS -- Does speed matter? For a number of years now, the top players in men's tennis have been dominant regardless of the surface and the conditions, and there is a consensus that differences in court speeds have decreased as part of a general slowing down of the game.

But variation still exists, and one player has been exploiting it very effectively the past nine months: Roger Federer. Although Novak Djokovic and Rafael Nadal justifiably have taken most of the headlines with their endeavors, Federer has been piling up titles, first during the quieter fall period and here and there this season when opportunity has knocked. Most, if not all, have come in quicker conditions, and even Federer's run to the French Open final last year was helped by the hot, sunny conditions and the new brand of balls that players described as faster and harder than the ones previously used.

So the state of play likely will affect Federer's prospects over the next two weeks, particularly if he plays against the top two. Do conditions this year help or hurt the Swiss? It's a mixed bag, based on his description: The courts are quick, particularly with the hot weather so far, but the balls are slower this year.

"I think the balls are heavy. I think they're slower than last year," Federer said after his first-round win. "Courts are on the harder side, especially when it's with good weather like today -- feels like it's faster."

Djokovic agreed. "Yes, the ball change is obvious," he said. "I think last year they were really fast and tough to control with conditions that are present in the Roland Garros, which are a little bit different from other clay-court events, and the conditions here are a little bit faster than maybe comparing to Monte Carlo or Barcelona or Rome."

Although the balls will remain the same, the court speed can be significantly affected by weather changes. When it's hot and sunny, the ball flies faster through the air, adding a little zing to the play and usually benefiting shot-makers and attack-minded players. If it turns cold, things slow down. Rain has the most dramatic effect. It can turn the courts into a swamp and weigh down the balls with moisture and sticky clay. Those were the conditions in which Federer lost to Robin Soderling in the 2010 quarterfinals, with the Swiss looking increasingly helpless and resigned to defeat as the rain fell.

"I'm not blaming the conditions or anything, but I think they were in his favor towards the end," Federer said, a little contradictorily, after that loss. "These were some serious, tough conditions, you know."

The current forecast suggests mercurial weather. The heat of the first few days is expected to give way to cooler conditions toward the end of the first week. Temperatures are then supposed to rise again as the second week begins, but rain is supposed to start falling midweek.

No matter how the court plays, Federer is not expected to have much trouble during the first week. He looked a little scratchy in his opening win after taking three days off after Rome, but all the seeds in his section have been cleared out, which means an opportunity to work out the kinks against fairly straightforward opponents -- Adrian Ungur, Martin Kuzan or Nicolas Mahut, then someone from a group consisting of David Goffin, Arnaud Clement, Lukasz Kubot and Florent Serra.

But with big hitters Juan Martin del Potro and Tomas Berdych in Federer's quarter and Djokovic in his half, slower conditions could leave Federer facing an uphill battle later in the event.

Then again, these things don't always follow a pattern. Federer's most successful clay-court event used to be the old Masters event in Hamburg, which was known for its cold, damp conditions. And some of his recent tournament success also can be explained partly by the absence, upset or subpar form of Djokovic and Nadal in addition to the Swiss' own sterling play.

Overall, however, Federer's record does imply that faster conditions give his game a boost against the current field. After losing to Djokovic in the U.S. Open semifinals from match point up, Federer went undefeated for the rest of 2011, winning two Davis Cup matches, his hometown tournament of Basel, the Paris Masters and the year-end ATP World Tour Finals. The Davis Cup tie was on grass, and the others were indoors in quicker conditions. This year, he swept through in Rotterdam, which was played under similar conditions, then went on to take more standard outdoor hard-court titles in Dubai and Indian Wells.

Then came the high altitude and slippery, new, blue clay courts of Madrid earlier this month, when Federer stood his ground and belted winners while Djokovic and Nadal flailed. The Swiss left the tournament with the trophy and the world No. 2 ranking. He didn't hold on to No. 2 long, as Nadal took it back the next week by winning on the more standard, slower, red clay courts in Rome. Still, the surge has put Federer back in the hunt for No. 1. Getting back on top of the rankings, even for a week, would allow Federer to tie Pete Sampras for the record of most weeks at No. 1 (286).

If he could pick, then, Federer probably would want the courts to play as fast as possible during the next two weeks. For Federer's French Open outlook, keep an eye on the weather forecast.