World No. 1 Rafael Nadal says he won't play at the Swiss Indoors in Basel starting on Monday.

On Friday, Nadal posted on his Facebook page a message saying: "sorry to announce that I won't travel to Basel in Switzerland but after very exhausting weeks I have to regroup my fitness and my body."

Nadal was sidelined for seven months after hurting his left knee in the summer of 2012.

But he came back strong and beat Novak Djokovic to win the U.S. Open in August for his 13th career Grand Slam title.

Since then, Nadal has played for Spain in the Davis Cup and lost to Djokovic in the final in Beijing and to Juan Martin del Potro in the semifinals in Shanghai last week.

Nadal says he will try to "come back to the Swiss Indoors next year."