Last year 's runner - up Rafael Nadal withdraws from the French Open . Spanish player has already missed European and North American events . He lost to Novak Djokovic in last year 's final in New Haven . Former world number one has a history of knee problems .
Last year 's runner-up Rafael Nadal withdraws from the U.S. Open . Spanish player has already missed Olympics and North American events . Nadal lost to Novak Djokovic in last year 's final in New York . Former world number one has a history of knee problems .