VINA DEL MAR, Chile — Rafael Nadal won his first of two matches Friday in a test of his sore left knee, defeating fellow Spaniard Daniel Gimeno-Traver 6-1, 6-4 to reach the semifinals of the VTR Open.

Nadal had not played for seven months before he took the court earlier this week in this Pacific coastal resort city. With a doubles match set for later Friday, Nadal will have played five matches in four days.

“I felt better today than the first day, so that’s a positive thing,” he said. “That’s a thing that gives me confidence and hope for the future that we’re going in the right way. After seven months out of competition, even if I don’t have the pain in the knee, at the beginning you feel slower, you feel more tired than usual so you need time to adapt. That’s the thing. I need time to do it. I still feel pain in the knee some days and that’s something we hope and think will be improving week by week.”

Nadal and Juan Monaco faced Argentines Carlos Berlocq and Leonardo Mayer later in the semifinals of doubles. Nadal plays Jeremy Chardy in the singles semifinals today.

The singles and doubles finals are Sunday, which also could be a busy day for Nadal.

The Spniard’s goal is to get back to the top and challenge the other three of tennis’ Big Four: Novak Djokovic, Roger Federer and Andy Murray.

Nadal took the court Friday with temperatures hovering around 85 degrees in the middle of the South American summer. He is likely to encounter similar temperatures when he plays next week in Sao Paulo, Brazil, and later this month in Acapulco, Mexico.

Nadal has said he’s not focusing on the results while he uses the Latin American clay-court events to hone his game. But most fans expect one of the most dominant clay-court players in history — he has won 93 percent of his singles matches on the surface — to win all three tournaments and show he’s ready to challenge for an eighth French Open title come May.

He will turn 27 in the middle of the French Open.

Nadal was asked Friday about testing for performance-enhancing drugs. He said he wants cheats caught, and clean athletes protected.

“Not everyone has to pay for some sinners,” Nadal said.

Nadal said earlier this week he had passed six blood and urine tests since losing on June 28 at Wimbledon — his most recent tournament before the current one in Chile.

Nadal, an 11-time Grand Slam winner, said it should be made public who is being tested and how frequently.

“If I go through a lot — or very few doping controls — people should know,” he said. “Though I went for seven months without competing, I went through a lot of tests.”

“I don’t have to justify anything,” he added. “This information should be open the public.”

All top tennis players are subject to being tested without warning. The admission last month by Lance Armstrong that he used banned substances in all seven of his Tour de France victories has increased the focus on doping in all sports.

“The important thing is that those who are cheating, pay for their cheating,” Nadal said.