"You keep on inspiring all of us, the sport needs you" - Novak Djokovic leads wishes for Roger Federer on Swiss' 40th birthday

World No. 1 Novak Djokovic was among a host of players who wished Roger Federer on his 40th birthday on Sunday.

In a video posted on the ATP Tour's social media handles, Djokovic said it was an "honor" to compete in the same era as Federer. The Serb also thanked the Swiss maestro for inspiring players on and off the court.

"40th? Wow, what a milestone," Djokovic said. "You keep on inspiring all of us on the court and off the court. It's been a huge honor to share the tennis court with you over the last 15 years, and hopefully, you can still keep on playing. The sport needs you. Thanks for showing us that even at that age we can play at a very, very high level."

"All the best, I wish you health and love and happiness with your close ones. Thanks again for everything," he added.

Japan's Kei Nishikori and Canada's Felix Auger-Aliassime also had warm words for Federer. Nishikori said he always considered Federer his idol and expressed his desire to see the Swiss win more Grand Slam titles.

Auger-Aliassime, meanwhile, lavished praise on the Swiss for his longevity and remarked that he too would like to be able to compete on tour at the age of 40.

"The big 40? Wow I'm just going to be turning 21," the Canadian said."I hope I'll be playing at the age of 40 as well. Thank you for everything you have been doing for tennis, it's so good to still have you around."

The full video can be seen below:

Forty-love 🎉 Happy Birthday to an icon & champion of our sport, @rogerfederer! 🎊🎈 pic.twitter.com/b78UopQrja

— ATP Tour (@atptour) August 8, 2021

Roger Federer's US Open participation in doubt

Roger Federer

After injury derailed his 2020 season, Roger Federer returned to action earlier this year. However, things have not gone according to plan for the 40-year-old. The Swiss played just six competitive matches heading into Wimbledon, where he was defeated handily by Hubert Hurkacz in the quarterfinals.

The 40-year-old subsequently withdrew from the Tokyo Olympics, as well as Masters 1000 events in Toronto and Canada, citing problems with his knee. His participation in the US Open is now very much in doubt.

Roger Federer out of Toronto and Cincinnati due to his knee injury.His US Open situation isn't looking ideal...

— José Morgado (@josemorgado) August 5, 2021

The Swiss will be hoping he can shake off the injury before the start of the final Grand Slam of the year. Given that Novak Djokovic and Rafael Nadal have moved level with Federer on 20 Majors, the Swiss will be keen to compete at Flushing Meadows to try and regain his lead in the Slam race.