Defending champion Rafael Nadal battled through a foot injury to beat Juan Martin del Potro and reach the quarter-finals at Wimbledon.
The Spaniard looked in real trouble when the doctor was called late in the first set, but he dug deep to win 7-6 (8-6) 3-6 7-6 (7-4) 6-4.
"At the end of the first set I thought I had to retire," top seed Nadal told BBC Sport afterwards.
He will play American Mardy Fish in the last eight on Wednesday.
Del Potro might be ranked 21st in the world but the 2009 US Open champion is rising fast after missing most of 2010 through injury, and is considered by many to be among the best five players in the world.
The size of Nadal's task was clear early on as Del Potro served his way out of trouble when facing four break points in the first set.
There was more trouble for the champion with the set poised to go to a tie-break as both the trainer and the doctor were called onto Centre Court to examine a problem with his left foot.
Del Potro was clearly unhappy with the delay and voiced his dissatisfaction to the umpire, but an official medical time-out was called and Nadal had his left foot retaped, having earlier removed the original bandage.
The Spaniard was moving gingerly at the start of the tie-break and fell 3-0 down, but showed the guts of a 10-time Grand Slam champion to haul himself back to save a set point and take it when Del Potro double-faulted.
If the world number one thought he had got his man, he was wrong, and Del Potro continued to dominate on his own serve before getting the first break of the day at 5-3 when Nadal went long, serving out to level the match.
With the contest finely balanced at 2-2 in the third set, it was Del Potro's turn to suffer an injury worry when he slipped badly while trying to change direction.
The Argentine had been forced to pull out of his last match against Nadal at the Madrid Open in May with a hip injury, and he looked to have damaged the same area as he limped off court for several minutes of treatment.
Serve continued to dominate when play resumed and, once again, it came down to Nadal's killer instinct in the tie-break as he moved ahead after two Del Potro errors gave him the advantage.
A classic Nadal whipped forehand finally gave him his first break of the day for 3-2 in the fourth set and, with the light fading and the Centre Court clock showing 2105 BST, the champion closed out a hard-fought win after three hours and 52 minutes.
Asked afterwards about his injury, Nadal added: "I don't know what the problem was yet. It seems like it was in the bone in the foot, I don't know how to explain exactly in English. I'm going to check it tomorrow.
"In the first set I thought I'd have to retire but the tape changed the position of the foot and when I pushed hard I was able to continue, but was in a little bit of pain.
"I have to check with the doctor here and my physio. I don't know tomorrow if I'll go to the hospital."