Favorites: Novak Djokovic (No. 1 seed)
Djokovic, the 2011 US Open champ, is attempting to capture his third Grand Slam title of 2015, having already won the Australian Open and Wimbledon. He could face Rafael Nadal in the quarters, last year's surprise finalist Kei Nishikori in the semis and Federer in the final.
“I think I would still put Novak there at the top of the list [of favorites],” reigning US Open champ Marin Cilic said.
Roger Federer (No. 2 seed)
Federer hasn’t been to the final here since 2009, but enters with great confidence after beating Andy Murray and Djokovic back-to-back to win in Cincinnati. A six-time US Open finalist between 2004-09, the Swiss has a 72-10 match record at the final Grand Slam championship of the year.
“A confident Roger Federer is fun to watch, and that’s what we have at the moment,” ESPN’s Darren Cahill said.
Andy Murray (No. 3 seed)
The 2012 Open champ comes into Flushing Meadows as the US Open Series men’s champion and will attempt to set a record for the largest payout in tennis history– $4.3 million. He faces controversial Australian Nick Kyrgios in the first round.
Stan Wawrinka (No. 5 seed)
The French Open champ has captured two majors since 2014, more than Federer and Nadal combined.
Rafael Nadal (No. 8 seed)
The Spaniard has won twice here (2010 and '13), but his physical style of play has taken a toll.
Marin Cilic (No. 9 seed)
Can he repeat last year's incredible performance and win again?
Favorite: Serena Williams (No. 1 seed)
History is on the line for the three-time defending champ as she seeks the first calendar Grand Slam since Steffi Graf in 1988. She is also looking to tie Graf with her 22nd career major title. "I love winning here, I love playing here and that’s all I want to do," she said.
Dark horses: Simona Halep (No. 2 seed)
The Romanian is No. 2 in the world despite having never won a Grand Slam title. She has never been past the 4th round in Queens, but appears to have a clear path to the final.
Victoria Azarenka (No. 20 seed)
The 2012 and 2013 Open finalist has fallen in the rankings, but may be Serena's biggest threat.
Follow Adam Zagoria on Twitter @AdamZagoria for updates throughout the U.S. Open.