Rafael Nadal
Seven-time French Open champion Rafael Nadal appeared shaky in his first two matches in Paris, but will have to find a new groove Saturday in the third round of the French Open. Reuters

No. 5 Rafael Nadal’s incredible return from injury may have hit its first wall.

The 26-year-old has won five tournaments already in 2013, but his last two matches have tested the knee that kept him out for seven months last year.

Nadal reached the semifinals of the Italian Open Friday after beating No. 4 David Ferrer 6-4, 4-6, 6-2, extending his winning streak to 12 straight matches.

That win came after Nadal’s first sign of trouble in the third round against Ernests Gulbis. Nadal completely dropped the first set 1-6, but rallied in the final two 7-5, 6-4. Following the match, questions about his knee injury bothered the Spaniard, but he also welcomed the challenge of falling behind early.

"I really don't want to talk about my knee. I'm fine. I (fought) a lot to be where I am today," Nadal said. "These matches like today where you're in trouble all the time but you keep fighting for every ball, this victory means a lot. To have another one like this is very special."

With the French Open just around the corner, speculation about just how healthy that shaky knee is may have been answered by the adjustment Nadal has made to his workouts. Nadal told reporters he has cut workouts down to 50 minutes a day over his usual two hour sessions.

Nadal has won seven of the last eight French Opens, taking advantage of his superior skills on clay. This year he’s 28-2 on clay, and hiscareer winning percentage of .930 on clay is unmatched by his contemporaries.

Several of the top players in the world also appear to be slipping, which could only help Nadal’s chances. A lower back injury suffered by No. 2 Andy Murray has put his status for Roland Garros in jeopardy, while Novak Djokovic lost his three-set quarterfinal match to Tomas Berdych Friday, and doesn't appear to as dominant as he was last year.

Berdych is next up for Nadal in the semifinals in Rome this weekend.