WIMBLEDON, England (AP)—Stretching to hit a forehand, Rafael Nadal slipped on the worn turf behind the baseline. He felt a crack behind his right knee and hopped away from the net after losing the point.

The fourth-round match at Wimbledon was in only the second game, and Nadal feared a serious injury.

He requested immediate treatment from a trainer, who examined and stretched his leg, then wrapped it below the knee.

Once back on his feet, that was the last sign of distress from Nadal, who beat Mikhail Youzhny on Monday, 6-3, 6-3, 6-1.

Nadal conceded he had been worried.

“I felt a little bit pain,” the Spaniard said. “I was a little bit scared because I felt something.

“I think I am fine. I don’t have a lot of pains. Like every professional sportsman, (we) have pain because … we go to the limit, no?”

Nadal is trying to become the first man since Bjorn Borg in 1980 to win the French Open and Wimbledon in the same year. He remains on course to meet top-ranked Roger Federer in the final for the third year in a row, and he’s scheduled to face Andy Murray of Scotland in the quarterfinals Wednesday.

“Right now I am feeling better,” Nadal said. “Tomorrow we will see how I wake up, but hopefully it’s going to be fine.”

Nadal is 3-0 against Murray, but they have never met on grass. And never in front of 15,000 partisan fans on Centre Court.

Murray is trying to become the first British man to win Wimbledon since Fred Perry in 1936.

“I know if I play against Andy Murray, probably the crowd is going to be with him,” he said, before adding optimistically: “I think with me it’s going to be nice, too, no?”

Federer’s progression was carefree. As in the previous three rounds, he didn’t drop a set.

With 21 aces, Federer beat 2002 champion Lleyton Hewitt 7-6 (7), 6-2, 6-4. Federer, seeking his sixth successive Wimbledon title, extended his winning streak on grass to 63 matches, including 38 in a row at the All England Club.

His last grass-court loss came in the first round at Wimbledon in 2002 against Mario Ancic. And that is his next opponent.

“I completely underestimated him back in 2002 when I played him,” Federer recalled. “I played a great Wimbledon the year before … I just thought, `I’ll play a little bit of serve and volley. I expected him to stay back.’ And it was the opposite.

“I couldn’t serve and volley because I thought conditions were slow. He served and volleyed first and second serves almost, I can remember. I got completely surprised. He played well until the very end. I was a little shellshocked and didn’t know what happened to me.”

Ancic said he won’t be facing the same Federer as in 2002.

“I can sit here and talk stories about how great a win it was and how I beat Roger Federer, but actually it wasn’t Roger Federer as we know him today,” Ancic said.