Men's Grand Slam singles record-holder Roger Federer said Wednesday he would be sidelined until 2021 after undergoing keyhole surgery on his right knee. The Swiss said he needed follow-up arthroscopic surgery "a few weeks ago" after undergoing a similar procedure in February.

Federer, whose last Grand Slam win was the 2018 Australian Open, said he "experienced a setback during [his] initial rehabilitation". 

"I plan to take the necessary time to be 100 percent ready to play at my highest level," the 38-year-old said in a statement on Twitter.  

"I will be missing my fans and the tour dearly but, I will look forward to seeing everyone back on tour at the start of the 2021 season." 

Following his semi-final loss to eventual champion Novak Djokovic at the Australian Open back in January, the 20-time Grand Slam singles champion hasn't set foot on the tennis court.  

The World No.4 was planning to make a comeback at Wimbledon, which was canceled later due to the COVID-19 pandemic.  

(With input from agencies)