Reigning US Open champion Stan Wawrinka announced Friday that he will not be in New York to defend his title because of a season-ending knee injury.

In a post on his Facebook page and an official announcement from his team, the three-time Grand Slam men’s singles winner said he is setting his sights on a return to the court in 2018.

“I am sad to announce that, after talking with my team and doctor, I had to make a difficult decision to undergo a medical intervention on my knee," Wawrinka said. "This was the only solution to make sure I will be able to compete at the top level for many more years.

“This is obviously extremely disappointing, but I’m already looking ahead and planning my recovery. I love this sport and I will work hard to get back to my top level and play many more years. I also want to take this opportunity to thank my fans for sending plenty of messages of support during the last couple of days. I will see you all in 2018!”

The Swiss is the second former champion to pull out of the US Open in as many weeks, following Novak Djokovic's withdrawal with an elbow injury on July 26.

The absence of Djokovic and now Wawrinka means the 2017 US Open, which begins on Aug. 28, will feature neither finalist from the previous year for the first time in almost half a century. In 1970, Ken Rosewall defeated Tony Roche in an all-Australian final, but neither played in the Big Apple the following year.

The announcement comes just two days after Wawrinka withdrew from the US Open Series events in Montreal and Cincinnati.

Andy Murray, Rafael Nadal and Roger Federer are currently in line to be the top three seeds, with 2014 champion Marin Cilic in line to be seeded fourth, based on the current rankings.

Wawrinka, 32, is currently ranked fourth in the world, but he will now slip down the rankings since he is unable to defend the 2,000 points he won at the US Open in 2016. It also means he will not have a shot at claiming his fourth major title in as many years, following the Australian Open in 2014 and Roland Garros in 2015.

Germany's Florian Mayer has moved into the main draw.