By Piers Newbery
BBC Sport at Wimbledon
Nadal needed treatment but was never in danger of losing the match
Roger Federer and Rafael Nadal both reached the quarter-finals at Wimbledon with straight-sets wins - despite an injury scare for Nadal.
Defending champion Federer eased past Lleyton Hewitt 7-6 (9-7) 6-2 6-4, without ever hitting the heights on a sun-drenched Centre Court.
And second seed Nadal overcame a knee injury that required treatment from the doctor to beat Mikhail Youzhny.
He recovered to beat the Russian 17th seed 6-3 6-3 6-1 on Court One.
Nadal had little trouble in seeing off Youzhny, breaking twice in the first and second sets and saving three break points at the start of the third.
The real drama came as early as the second game when Nadal slipped at the back of the court and tweaked his right knee, requiring treatment from the trainer and the doctor at the changeover.
I felt a little bit of pain and was a little bit scared because I felt something crack, but it's fine now
Nadal appeared to be limping in the following game but nothing seems to disrupt the 22-year-old and he powered on, even hitting top form in the third set.
The Mallorcan, who faces Andy Murray in the last eight after the Briton beat Richard Gasquet in a five-set marathon, played down concerns about his knee.
"It's nothing very important that's for sure. I felt a little bit of pain and was a little bit scared because I felt something crack, but it's fine now," he said.
"It was a very good result for me. I played a very good match and I am happy with the way I am playing and that I am in the quarter-finals."
On another glorious day in south west London, Federer reached the quarters with a comfortable win over Hewitt.
The Australian put up a good fight in a first set in which there were no break points, and Federer needed four set points before taking the tie-break.
The top seed then broke twice at the start of the second and raced away to win in one hour 48 minutes.
He hit every line out there with his serve today
He will play Croatia's Mario Ancic after the Mario Ancic beat Spain's Fernando Verdasco in five sets.
It was far from a flawless performance from Federer and he struggled to put away Hewitt - struggling with a hip injury - in the first set, thumping a forehand long on one of four set points.
But once he finally wrapped it up with an ace there was only going to be one winner - as there had been in the last 11 meetings between the pair.
Federer faced break points in four successive games at the end of the second and start of the third sets, but always raised his game when it mattered and never seemed unduly worried.
The Swiss had saved eight break points but got a crucial break of his own in game three of the third.
That was the decisive blow and Federer sealed victory soon after with yet another heavy serve that Hewitt could not return.
"I'm just happy the way I'm playing," said Federer. "No real problems so far. I've been serving well.
"I've been playing well, beating dangerous opponents, such as (Robin) Soderling and now Lleyton. I think Lleyton was a tough draw to get in the fourth round."
Hewitt admitted: "He hit every line out there with his serve today. That's why he's the best player going around, especially on this surface. Serve is so important. He hit the target every time.
"I had a few break-point chances there late in the second set and early in the third set. I didn't do too much wrong with them.