World number one Rafael Nadal will miss Spain's Davis Cup final against Argentina this month after failing to recover from tendonitis in his knee.
Nadal said it had been an extremely difficult decision and he had done everything possible to get fit.
"I am used to playing with pain but this was a new and different pain I cannot control," he said in a statement on his website (www.rafaelnadal.com).
The injury forced Nadal to pull out of the season-ending Masters Cup in Shanghai which began Sunday and he also had to retire from his Paris Masters quarter-final against Nikolay Davydenko last month.
The Spanish tennis federation is expected to name its team Tuesday for the tie in Mar del Plata from November 21-23.
The French Open and Wimbledon champion has previously blamed his injury on an overloaded tennis calendar.