GettyImages-1019631566
Roger Federer can expect a tough road to the U.S. Open final in 2018. Rob Carr/Getty Images

Roger Federer continues to chase Grand Slams but at age 37 appears to be acutely aware that his fitness is an issue against other well-established and hungry players on the ATP tour. When the U.S. Open begins Monday, Federer will be considered an underdog to take home a title that has eluded him for a decade.

According to betting site OddsChecker, Novak Djokovic, who defeated Federer in Cincinnati, 6-4 6-4, is the favorite to win at Flushing Meadows at 5/2 odds. Djokovic is followed by defending champion Rafael Nadal, who is listed at 57/17 odds. Federer has the third-best shot at 6/1, but is well ahead of Alexander Zverev, who has the fourth-best odds at 12/1.

“I’m not the favorite — they are: Rafa and Novak, in my opinion,” Federer said Sunday after his defeat to Djokovic. “But I’m happy that my level is there. I just need to figure out my game, get used to different balls.”

While Federer has overcome some nagging injuries and struggled with his footwork at times this year, he is still enjoying an excellent year by any standard. The world No. 2 has won three titles this year, including the Australian Open, and boasts a 33-5 record and $5.6 million in prize money.

There is a tough path to a Grand Slam awaiting Federer in New York. He could meet Nick Kyrgios in the third round, Djokovic in the quarterfinals, Marin Cilic in the semifinals and Nadal in the final.

Federer has won five U.S. Open titles but the tournament represents his longest Grand Slam drought. Federer won his only French Open in 2009 but his last U.S. Open championship came in 2008. Over the past decade, he has two finals and three semifinals appearances.

The Swiss legend, who has 20 Grand Slams on his prestigious resume, has expressed optimism about the level of play that can be expected in New York.

"I think it will be a very exciting end to the season because everybody’s going to probably be healthy or healthier again," Federer said about the upcoming tournament.

Tennis legend John McEnroe has echoed the importance of this year's tournament and told the Washington Post that this is a "historic time" for tennis and the U.S. Open, with Federer, Djokovic, Nadal and the return of Andy Murray.

“This is the situation where the No. 1 ranking is going to be at stake," McEnroe said. "It’s got a lot of ramifications for where the fallout is in the future for those guys. If Rafa were to win this, he’d be closer to Roger. If Djokovic were to win, he’d be closer to Rafa. If Roger would win it at 37, he would set a new standard, add to his record of slams.

"This is a pretty exciting tournament for us.”