Defending champion Rafael Nadal overcame a spirited challenge from Mardy Fish to set up a Wimbledon semi-final against Britain's Andy Murray.
The world number one eased through the first two sets before Fish showcased his grass-court pedigree in the third.
Nadal won 6-3 6-3 5-7 6-4 but admitted the foot injury he suffered in Monday's win against Juan Martin del Potro was troubling him.
"It is not fine but this is Wimbledon, it's an emergency," he said.
"It's my last big tournament for a month-and-a-half so I'm not worried. We've done tests and they didn't show anything important.
"I have pain in the foot, I cannot run in perfect condition, but the anaesthetic means I can't feel pain for five hours."
The Spaniard suggested he would be "fine" to face Murray, who he beat in straight sets at the same stage 12 months ago.
Nadal is now unbeaten in 19 matches at SW19, dating back to his defeat by Roger Federer in the 2007 final, and can look forward to a 16th Grand Slam semi-final.
"I started the first two sets playing very well but made mistakes in the third and lost my intensity," the 25-year-old added.
"But I started playing more aggressively and I'm very happy to be in the semi-finals.
"It's always an honour to play against Andy, he has played fantastic in the last few months.
"He is playing well here and it's always a pleasure to play him. We play Playstation a lot outside the court and we are good friends."
Nadal arrived on Court One with question marks surrounding his physical state but showed little discomfort in breaking Fish in game one and again for 5-2.
The American 10th seed recovered one of the breaks when Nadal sent a forehand wide but then miscued a forehand of his own to concede the 36-minute opener.
It was a similar story in the second set as Fish squandered two break points in game three and was punished as his opponent moved 3-1 ahead.
Two love service games and a hold to 15 put Nadal in total control and seemingly on course for a routine victory.
However, Fish began striking the ball with greater power and depth while also coming into the net at every opportunity.
Breaks were exchanged early in the third set before the 29-year-old made his move in game 12 with a sumptuous forehand winner.
His hopes of reaching a maiden Grand Slam semi-final were alive - but only briefly. Nadal produced a majestic drop volley to gain break points in game three of the fourth and Fish netted a backhand to relinquish the momentum.
Nadal was imperious thereafter and a hold to love sealed the win in two hours and 53 minutes.
"There's not much I'd have done differently," stated Fish. "I'd never played on that court before, it takes a while to get used to.
"I started hitting the ball really well in the third set and got my teeth into the match. But I missed a ball in the shadows to get broken.
"It's not a bad loss by any means but further than the quarters is where I want to go. I'm lacking that one huge result that opens everyones eyes and says 'wow, can't believe you beat him'."