![Novak Djokovic (Serbia) in action during round 4 of US Open Championship against Stan Wawrinka (Switzerland) at Billie Jean King National Tennis Center (Photo by Lev Radin/Pacific Press/Sipa USA Stock Photo - Novak Djokovic (Serbia) in action during round 4 of US Open Championship against Stan Wawrinka (Switzerland) at Billie Jean King National Tennis Center (Photo by Lev Radin/Pacific Press/Sipa USA Stock Photo -](https://c8.alamy.com/comp/2ENKX9P/novak-djokovic-serbia-in-action-during-round-4-of-us-open-championship-against-stan-wawrinka-switzerland-at-billie-jean-king-national-tennis-center-photo-by-lev-radinpacific-presssipa-usa-2ENKX9P.jpg)
Novak Djokovic (Serbia) in action during round 4 of US Open Championship against Stan Wawrinka (Switzerland) at Billie Jean King National Tennis Center (Photo by Lev Radin/Pacific Press/Sipa USA Stock Photo -
![Runner-up Novak Djokovic of Serbia L and US Open 2016 Champion Stanislas Wawrinka of Switzerland during Trophy Presentation Editorial Photography - Image of sports, national: 89113317 Runner-up Novak Djokovic of Serbia L and US Open 2016 Champion Stanislas Wawrinka of Switzerland during Trophy Presentation Editorial Photography - Image of sports, national: 89113317](https://thumbs.dreamstime.com/z/runner-up-novak-djokovic-serbia-l-us-open-champion-stanislas-wawrinka-switzerland-trophy-presentation-new-york-89113317.jpg)
Runner-up Novak Djokovic of Serbia L and US Open 2016 Champion Stanislas Wawrinka of Switzerland during Trophy Presentation Editorial Photography - Image of sports, national: 89113317
![Roger Federer of Switzerland hits a forehand to Novak Djokovic of Serbia in the Mens Semifinal at the U.S. Open Tennis Championships in Arthur Ashe Stadium in New York City on September Roger Federer of Switzerland hits a forehand to Novak Djokovic of Serbia in the Mens Semifinal at the U.S. Open Tennis Championships in Arthur Ashe Stadium in New York City on September](https://c8.alamy.com/comp/TYM18N/roger-federer-of-switzerland-hits-a-forehand-to-novak-djokovic-of-serbia-in-the-mens-semifinal-at-the-us-open-tennis-championships-in-arthur-ashe-stadium-in-new-york-city-on-september-11-2010-upijohn-angelillo-TYM18N.jpg)
Roger Federer of Switzerland hits a forehand to Novak Djokovic of Serbia in the Mens Semifinal at the U.S. Open Tennis Championships in Arthur Ashe Stadium in New York City on September
![Stan Wawrinka (Switzerland) in action during round 4 of US Open Championship against Novak Djokovic (Serbia) at Billie Jean King National Tennis Center (Photo by Lev Radin/Pacific Press/Sipa USA Stock Photo - Stan Wawrinka (Switzerland) in action during round 4 of US Open Championship against Novak Djokovic (Serbia) at Billie Jean King National Tennis Center (Photo by Lev Radin/Pacific Press/Sipa USA Stock Photo -](https://c8.alamy.com/comp/2ENKX8H/stan-wawrinka-switzerland-in-action-during-round-4-of-us-open-championship-against-novak-djokovic-serbia-at-billie-jean-king-national-tennis-center-photo-by-lev-radinpacific-presssipa-usa-2ENKX8H.jpg)
Stan Wawrinka (Switzerland) in action during round 4 of US Open Championship against Novak Djokovic (Serbia) at Billie Jean King National Tennis Center (Photo by Lev Radin/Pacific Press/Sipa USA Stock Photo -
Stan Wawrinka of Switzerland hugs Novak Djokovic of Serbia at the net... Nachrichtenfoto - Getty Images
![Roger Federer of Switzerland follows through on a backhand to Novak Djokovic of Serbia during their men's singles final match at the U.S. Open Championships tennis tournament in New York, September 13, Roger Federer of Switzerland follows through on a backhand to Novak Djokovic of Serbia during their men's singles final match at the U.S. Open Championships tennis tournament in New York, September 13,](https://c8.alamy.com/comp/2CK0M0Y/roger-federer-of-switzerland-follows-through-on-a-backhand-to-novak-djokovic-of-serbia-during-their-mens-singles-final-match-at-the-us-open-championships-tennis-tournament-in-new-york-september-13-2015-reutersshannon-stapleton-2CK0M0Y.jpg)