Rafael Nadal of Spain reacts during his men's singles tennis match against Nick Kyrgios of Australia at the Wimbledon Tennis Championships, in London, July 1, 2014. [Photo/Agencies]

Reigning champion Rafael Nadal pulled out of the US Open because of an injury for the second time in three years Monday, leaving Novak Djokovic and Roger Federer as the men to beat at the year's last Grand Slam tournament.

Nadal announced his withdrawal, blamed on a bad right wrist, one week before play begins at Flushing Meadows.

"I am sure you understand that it is a very tough moment for me since it is a tournament I love and where I have great memories from fans, the night matches, so many things," a posting on Nadal's Facebook page read. "Not much more I can do right now, other than accept the situation and, as always in my case, work hard in order to be able to compete at the highest level once I am back."

The second-ranked Nadal plays left-handed, but he uses a two-handed backhand.

The 14-time major champion was hurt July 29 while practicing on his home island of Mallorca ahead of the North American hard-court circuit. The next day, Nadal announced he needed to wear a cast on his wrist for two to three weeks and would be sitting out tournaments in Toronto and Cincinnati.

The 28-year-old Spaniard also said at that time he expected to return for the US Open.

Instead, he's the fourth man in the Open era, which began in 1968, to decline to try to defend his US Open title. The others were Ken Rosewall in 1971, Pete Sampras in 2003 and Juan Martin del Potro in 2010. Del Potro also is out of this year's US Open after wrist surgery in March.

Nadal is 44-8 with four titles in 2014, including his record ninth French Open trophy in June. He has not competed since losing in the fourth round of Wimbledon on July 1.