Novak Djokovic has challenged Serena Williams to return to tennis at the age of 43 after the American delivered a speech at Maria Sharapova's Hall of Fame induction.
Williams hasn't played professionally since losing to Ajla Tomljanovic at the US Open three years ago.
However, she's not officially announced her retirement and her older sister, Venus, is still going strong at the age of 45.
Recently, Williams showed class by giving a speech at Sharapova's Hall of Fame induction.
Novak Djokovic has challenged Serena Williams to return to tennis at the age of 43 after the American delivered a speech at Maria Sharapova's Hall of Fame induction
|GETTY
The Russian, who won five majors during her own career, previously retired in February 2020.
In the early hours of Monday morning, Djokovic overcame Learner Tien in straight sets to make the second round of the US Open.
Then, speaking in his post-match press conference, he opted to 'challenge' Williams by urging her to return to the court.
"It was great. It was a wonderful moment, and I think Maria (Sharapova) deserves it," he said.
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Next up for Djokovic is clash with Zachary Svajda.
Svajda, as an American, will have the backing of the home crowd in New York.
Djokovic was brilliant during his opening match but did appear to struggle with a foot issue.
Footage showed a huge blister forming, something that was clearly causing the 38-year-old some discomfort.
Djokovic was, however, quick to downplay the severity of his foot problem.
"I started great. Just over 20 minutes, first set, I felt really good. Then some long games to start the second set," he said.
"Then I start to feel really...I don't know why. I really was surprised how bad I was feeling in the second physically.
"Yeah, we had long exchanges, but also, I kind of dropped my level and made a lot of unforced errors and kind of got him back into the match.
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Novak Djokovic battled a painful blister during his US Open win in the early hours of Monday morning
|REUTERS
"[The] good thing, two days off now, but it’s slightly a concern.
"I don't have any injury or anything. I just struggled a lot to stay in long exchanges and recover after points."