Injured world number one Rafael Nadal pledged to do everything in his power to get fit in time for Spain's Davis Cup final against Argentina in just over two weeks.
Nadal has tendinitis in his right knee and was forced to pull out of the season-ending Masters Cup in Shanghai which begins on Sunday. He also had to retire from his Paris Masters quarter-final against Nikolay Davydenko last week.
"I will try everything to be at the Davis Cup but my participation depends on my progress," the French Open and Wimbledon champion told Marca radio on Wednesday.
"If I am only at 40 percent I won't go," he added. "I have a few days to recover and I will try to train a bit."
The Spanish tennis federation (RFET) said on Tuesday Nadal needed a week of rest and treatment and the Mallorcan said he would have a final test at the start of next week to determine whether he can represent Spain in Mar del Plata from Nov. 21.
He reiterated his criticism of the packed ATP tennis calendar, saying it was "very badly organised".
"It's very hard to always be at the highest level with a calendar like that," he said.
"I didn't say no to Shanghai, it was my knee. Going there would have been a very big effort."
Nadal will be replaced at the Masters Cup by Frenchman Gilles Simon, who will play world number two Roger Federer in the Swiss top seed's opening match.