Vina Del Mar, Chile - After seven months away treating a left knee injury, Rafael Nadal left many questions unanswered in his comeback tournament.

Nadal lost both the singles and doubles finals in the space of a few hours Sunday at the VTR Open in Chile. And Horacio Zeballos, who earned the first title of his career by beating Nadal in three sets, repeated what Nadal has been saying.

"Not playing has hurt him," Zeballos said. "Four or five tournaments back should get him back in form. I'd say this was the perfect time to play Rafa considering the confidence factor and everything."

In the final, Zeballos served better, hit more cross-court winners from sharp angles, and was quicker on clay than the Spaniard, the seven-time French Open champion who was introduced throughout the tournament as "The King of Clay."

Nadal said the loss was a reminder of what he already knew: returning to challenge the other three in tennis' top four - Novak Djokovic, Roger Federer and Andy Murray - will be slow and gritty.

"It was a week when we didn't know how the body would respond, the knee," Nadal said. "At least we have seen we can compete up to a certain level. It's true I have had good days and bad days that impact on my play. The tennis aspect isn't the most important thing. The most important was being out there again in front of fans.

"But I won't deny I wanted to win here."

Despite the positive spin, Nadal lost to a player he beat in straight sets three years ago in the French Open - 6-2, 6-2, 6-3. Nadal has won 50 tournaments on all surfaces, and Zeballos now has won one. Nadal has $50 million in tournament earnings, while the Argentine has a mere $1.3 million.

Nadal moves this week to the Brazil Open in Sao Paulo, an event that provides another test on his road to the French Open. He competes again on clay later this month in Acapulco, Mexico.

Nadal looks slimmer than before, and his powerful forehand appeared to be recovering faster than his serve and backhand.

The torn tendon in Nadal's left knee drew repeated questions. He said it's better some days than others, and there's still pain. He's avoided surgery, and he says he's been told by doctors the soreness may linger for a few more weeks - even a few months.

He wore a white bandage on the knee whenever he played, racing down plenty of loose balls and showing no signs of protecting the knee or, for that matter, his right knee, which has also been injured.

"Every day improves and increases the confidence for me," he said. "Every day that the knee answers well is a lot of positive energy for me, and that's helping me a lot. The feeling day by day is better - the feeling on court. ... I still feel pain in the knee some days, and that's something we hope and think will be improving week by week."