Roger Federer had to overcome a back injury and the rain to beat Xavier Malisse in the Wimbledon fourth round.
The six-time champion had treatment during the first set, but sealed a 7-6 (7-1) 6-1 4-6 6-3 win after a 40-minute delay for rain.
"My back is OK, it started to feel better as the match went on," Federer told BBC Sport.
World number one Novak Djokovic is also through to the last eight after beating Viktor Troicki in straight sets.
The Serb wasted little time in hammering his compatriot in 90 minutes, 6-3 6-1 6-3, to book a quarter-final meeting with either Richard Gasquet or Florian Mayer, who will complete their rain-interrupted match on Tuesday.
"It's never straightforward," Djokovic told BBC Sport. "You want to focus on every point because, at this stage the matches are getting more difficult. I think I played really well throughout the whole match.
"We know each other so well, the first match we played against each other I think he was nine years old and I was eight. It's never easy to play your good friends but there has to be a loser."
Federer, meanwhile, will meet 26th seed Mikhail Youzhny in the last eight after the Russian overcame Denis Istomin 7-5 in the fifth set.
The Swiss will be playing in his 33rd consecutive Grand Slam quarter-final.
After having to come from two sets down to beat Julien Benneteau in round three, Federer again looked in trouble as he left Centre Court for medical attention when 4-3 up in the opening set.
He returned to breeze through a tie-break and, after the rain, broke the serve of his Belgian opponent on three occasions in the second set.
But Malisse, the world number 75, hit back courtesy of a solitary break in the opening game of the third set.
He repeated the dose in the fourth, however Federer was not be taken to a decider, levelling things up then going 4-2 up with a decisive break that ultimately sealed his 850th career win.
"The back injury come and goes," he added. "When you play on tour for over 15 years the back does hurt at times, you just hope it doesn't come in a big match. It was scary, but the treatment was a big help."
"I'm very pleased that I came through, the rain delay helped me. I had to apologise to Xavier, it's a freak thing that happened.
"I've been doing exercises for years. I have a pretty good record with being injury free, so if this is the worst then I'm happy. I should be back fine on Wednesday."