Defending U.S. Open champion Rafael Nadal might not be able to hold onto the last grand slam title this year after sustaining a wrist injury in practice Tuesday.

The leftie Nadal, who won the recent French Open title, uses both hands when delivering a backhand.

Nadal, 28, will have to wear a cast on his right wrist for the next two to three weeks which forced him to withdraw from two U.S. Open tune-ups at Toronto and Cincinnati Wednesday.

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Nadal is also the defending champion of the Rogers Cup in Toronto, slated to start Monday, and the Cincinatti Open which starts the following week.

Nadal's manager Benito Perez-Barbadillo said doctors are monitoring Nadal's wrist with a series of MRI tests and will decide later whether he is fit to play at the U.S. Open in Flushing Meadows.

In a recent Facebook post, Nadal expressed his disappointment of being unable to defend his Rogers Cup title this year but expects to be well in time for the U.S. Open which begins August 25.

Nadal also released a statement to the Rogers Cup organizers stating that he injured himself during practice and will stay out of competition over the next two to three weeks.

The Toronto event won't disappoint though because World No. 1 Novak Djokovic and 17-time grand slam champion Scottish Roger Federer. Canadian Milos Raonic will also be participating in the tournament and will heavily be a crowd favorite.

Nadal is seeded eighth at the Canadian tournament. But, since he is unable to play, 2013 Wimbledon champion Andy Murray will take over his slot and have the privilege of a first-round bye.

TagsNovak Djokovic, Roger Federer, andy murray, Milos Raonic, tennis, U.S. Open