Today marks day five of classes and day five of the U.S. Open. Can Roger Federer win his sixth U.S. Open in a row and his first grand slam as a father? Will Rafael Nadal rediscover his pre-injury form? Can Andy Murray be one match better than last year? What about a resurgent Andy Roddick? Here’s the inside scoop.

The Favorite: Roger Federer

When last semester ended, Federer dropped to No. 2 in the world and was falling fast. Two grand slams and 26 match wins (in 27 matches) later, Federer is back to the top ranking and in fine form. He was so dominant at the Western & Southern Financial Group Masters two weeks ago that Novak Djokovic said, “The closest I was going to get to the first-place trophy is now,” during the trophy presentation. With the “Federer Express” picking up steam, book him for his 16th career major.

The Contenders:

Andy Murray: Murray, the newly minted world No. 2 as of Aug. 17, is having a great 2009 with a 50-7 record and five titles, including the Rogers Cup three weeks ago. Federer, in an interview with ESPN, praised Murray’s play. “He’s almost won everything there is to win,” the world’s top-ranked player stated. Perhaps, however, he was implying Murray still has yet to win a grand slam title. And the plot thickens.

Juan Martin del Potro: Del Potro beat Andy Roddick at the Legg Mason Tennis Classic and the Rogers Cup in back-to-back weeks, and in May, he took Federer the distance (five sets) at the French Open. This 20-year-old hits the ball with astonishing authority and is capable of bashing his way to the Open title. Roddick stated del Potro was “taking big cuts and connecting” in an interview with The Associated Press after their match at Legg Mason.

Andy Roddick: In his best season since 2004, Roddick has achieved his career-best results at the first three majors of the season, losing in the Australian Open semifinals and Wimbledon finals to Federer, and the French Open round of 16 to Gael Monfils. Wimbledon, in particular, was an incredible tournament for him, as he defeated Murray and took Federer to 14-14 in the fifth set before succumbing 16-14. Murray said in his BBC post-match interview after losing to Roddick that “When he serves like that he has a chance against anyone.” Except maybe Federer, whom he’s 2-19 against.

The Dark Horses:

Rafael Nadal: How did Nadal arrive here after becoming the world’s No. 1 and winning the Australian Open? Simple: he got tendonitis in his left knee, lost at the French Open for the first time ever and has lost in his last three tournaments before the finals, including a 6-1, 6-4 drubbing by Djokovic at Cincinnati. Clearly not healthy, he is a dark horse mostly based on reputation.

Novak Djokovic: Djokovic has struggled at the Grand Slams this year, getting upset early in the French Open and Wimbledon by Philipp Kohlschreiber and Tommy Haas, respectively, and getting outworked and outmaneuvered by a fitter Roddick in the Australian Open. Djokovic was a finalist in the 2007 U.S. Open, and if he can string together some good matches, he can be lethal again this year.

Jo-Wilfried Tsonga: Tsonga beat Federer at the Rogers Cup after being down 5-1 in the third and final set. Absolutely loaded with talent, he could very well put it all together and win the U.S. Open … or lose early.

Nikolay Davydenko: Davydenko is unheralded, despite being ranked in the top five each year from 2005 to 2008. Currently eighth in the world, Davydenko is as steady as they come and so is his solid baseline game.