After meeting in the 2016 U.S. Open final, both Novak Djokovic and Stan Wawrinka won't compete in the upcoming tournament. Getty

There will be a noticeable lack of star power ahead of the U.S. Open draw announcement on Aug. 25. On the women's side, six-time U.S. Open champion Serena Williams is shut down due to her pregnancy, while on the men's side, 2016 finalists Stan Wawrinka and Novak Djokovic are sidelined with injuries, which could potentially pave the way for surging Roger Federer and Rafael Nadal to capture another Grand Slam title this year.

Wawrinka, the defending champion, announced Friday on Facebook that he will undergo knee surgery and miss the rest of the 2017 season. The world No. 4 had reached the semifinals of the Australian Open and the final of the French Open but bowed out of Wimbledon in the first round.

Djokovic, who fell in four sets to Wawrinka in last year's final, pulled out of the U.S. Open and the rest of the 2017 season on July 26 because of an injured right elbow. After a highly successful 2016 season, the Serbian star has struggled mightily in 2017, dropping to No. 5 in the world rankings after failing to reach the semifinals of three Grand Slams.

With Wawrinka and Djokovic out, the odds have sharply improved for Federer and Nadal, two players that have captured all three Grand Slams this year. Wawrinka had the fourth-best odds of winning the U.S. Open a week before he withdrew.

Federer, who celebrates his 36th birthday Tuesday, has been on a hot streak in 2017, owning a stellar 31-2 record after a 21-7 record in 2016. Federer didn't compete at Flushing Meadows last year due to knee problems.

The Swiss legend saw his odds boosted to +110 after he was listed at +150, according to betting site Bovada.

Nadal, meanwhile, saw his title odds jump to +225 from +275. The clay-court specialist got his year off to an auspicious start by reaching the Australian Open final, falling in five sets to Federer in the hardcourt tournament, then later cruising to his 10th French Open title. The 31-year-old Spaniard, who won the U.S. Open in 2010 and 2013, is coming off back-to-back disappointing results in New York, losing in the third round in 2015 and the fourth round in 2016.

Andy Murray also remains firmly in the chase. The 2012 U.S. Open champion's odds (+400) have not budged despite the withdrawal of Djokovic and Wawrinka though he has mostly posted strong results in the tournament. The world No. 1, however, has failed to advance beyond the semifinals of any Grand Slam in 2017.

After Federer, Nadal and Murray, there is a long list of underdogs. Marin Cilic, the 2014 U.S. Open winner, has +1,400 odds and is followed closely by Milos Raonic at +1,600.