Since returning from his injury last month, the 11-time Grand Slam champion Nadal has won 12 of 13 matches in a South American clay-court swing, finishing runner-up in Vina del Mar, Chile, before taking titles in Sao Paulo and at the Mexican Open.

"Today I know I can play on clay. I will try next week on the hard," Nadal said. "Playing tennis will be a process to adapt my knee to the competition.

"I hope I will keep having the chances to play the normal calendar as I did in past years.

"I cannot predict the future. I have to see how the knee will last at Indian Wells next week. Having the chance to play at Indian Wells is great. I didn't know one week ago if I would be able to play at Indian Wells."

After Indian Wells, Nadal could play at a hardcourt event later this month at Miami, then switch to clay ahead of the French Open and grass for Wimbledon before facing hardcourts again in the run-up to the US Open.

Nadal tried out his knee on the hardcourts Monday night, playing an exhibition match against Argentina's Juan Martin Del Potro at New York's Madison Square Garden.

After two sets of hard-serving, steady rallies and the occasional moment of light-hearted fun, Nadal said he was ready to go.

"I am very happy," Nadal said. "It was a sad moment when I had to decide not come to the US Open. It seems like now everything is great."

Del Potro, who won the 90-minute match 7-6 (7/4), 6-4, said he was surprised at how quickly Nadal has returned to winning tournaments.

He predicted it won't be long before the left-handed Spaniard is challenging for another Grand Slam title.

"It is a good thing for everybody that Rafa is back," Del Potro said. "It is amazing how great he is playing. He is going to be fighting for No. 1 very soon."