Tennis - Djokovic faces now-or-never moment at U.S. Open

FILE PHOTO: Aug 31, 2020; Flushing Meadows, New York, USA; Novak Djokovic (SRB) serves the ball against Damir Dzumhur (BIH) on day one of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Robert Deutsch-USA TODAY Sports

(Reuters) - Novak Djokovic hesitated to call the U.S. Open a now-or-never moment, but the history-hunting Serb noted on Friday that an opportunity for a calendar year Grand Slam could be one of them.

The fact that only two male tennis players - Rod Laver and Don Budge - have ever achieved the feat underscores just how rare such moments are.