Rome, May 17: Roger Federer has suffered a potentially significant leg injury just nine days out from the French Open and has withdrawn from the Internazionali d'Italia.
The world number three had been due to face Stefanos Tsitsipas in the quarter-final in Rome on Friday (May 17).
A statement on the tournament's website said: "Roger Federer has just phoned the ATP supervisor and tournament director to announce his retirement due to a problem with his right leg."
Federer, whose only French Open title came a decade ago, had been hoping to build up some momentum on clay courts ahead of his first appearance at Roland Garros since 2015.
Federer plays down Kyrgios suspension talk
Earlier, Federer insisted Nick Kyrgios should not be suspended for his meltdown on Thursday.
A furious Kyrgios defaulted his second-round match against Casper Ruud after receiving a game penalty for throwing a folding table onto the court.
The Australian smashed his racquet and launched a table before walking off after shaking hands with Ruud and the chair umpire.
However, Federer said a fine and forfeiture of prize money and rankings points were punishment enough for Kyrgios.
"I don't think he should be suspended personally," Federer said after edging Borna Coric in the last 16.
"He walked off the court. What did he do? He hurt a chair? I mean, that's not enough for me.
"I don't know if he's on probation or not from his Shanghai thing or not.
"If that's the case, then obviously you can maybe look into it. If that's run its course, I don't think he should be suspended.
"A zero pointer, fine, all this stuff is already tough enough. He knows it's a mistake what happened."
Kyrgios' clash with Ruud was early in the third set when the 24-year-old defaulted.