In a statement posted on social media, the world No. 4 said he had been suffering “much more than I should” with a foot injury, adding that the decision to end his 2021 season was “the way forward to recover and recover well.”The Spaniard, who has a record-equaling 20 grand slam titles to his name, announced in June that he wouldn’t be taking part at Wimbledon and the Tokyo Olympics, saying he wanted to “prolong my career and continue to do what makes me happy.”Nadal’s last outing on a tennis court was at the Citi Open in Washington DC earlier in August where he suffered a shock loss in the round of 16 to South Africa’s Lloyd Harris.His announcement comes just days after Roger Federer said he would also miss the US Open to undergo another knee surgery which will sideline him for “many months.”Defending champion Dominic Thiem also pulled out of Flushing Meadows and will miss the remainder of the season citing a wrist injury. The 27-year-old star said on Wednesday that he hasn’t recovered from the injury he sustained at the Mallorca Open in June, which was the last tournament he played before withdrawing from Wimbledon and the Tokyo Olympics earlier this summer.In the absence of Nadal, Federer and Thiem, the road looks smoother for Djokovic as he aims to claim a memorable calendar slam — winning all four grand slams in the same calendar year. The Serbian, who is also seeking a record-breaking 21st grand slam singles title, failed in his search for a historic golden slam in men’s tennis at the Tokyo 2020 Olympics — winning all four grand slams and an Olympic gold medal in the same 12 months — losing in the semifinals. Visit CNN.com/sport for more news, features, and videosIf he was to win in New York, he would become the first player in men’s singles tennis to complete a calendar slam since Rod Laver did it a second time in 1969. This year’s US Open is scheduled to start on August 30 and runs through September 12 in New York.