World number one Roger Federer has torn a ligament in his right ankle and will miss next week's Madrid Masters.
Federer hopes to be fit for the season-ending Masters Cup
Federer has also pulled out of the following week's Swiss Indoor ATP tournament in his home town of Basel.
The 24-year-old missed last year's event in Basel after rupturing a thigh muscle on the tournament's opening day.
He told his website: "I'm extremely disappointed that I can't play at home for a second year, but I hope to be fit for the Masters Cup in Shanghai."
The season-ending event in China begins on 13 November.