"I started serving better and in the end it was just a matter of a few points here and there".
For the entire fifth set up to the deciding game, both men held serve.
One key: Nadal converted only 2 of 16 break points.
Overall, Nadal went a mere 2-for-16 on break points, while his fellow left-hander was a considerably better 3-for-8.
The Spaniard, a 15-time Grand Slam victor, came from two sets down to level the match, but was ultimately beaten 3-6, 4-6, 6-3, 6-4, 13-15 by the 16 seed after 4 hours and 48 minutes - the longest match of this year's tournament so far.
Andy Murray booked his place in the quarters with a 7-6 (1), 6-4, 6-4 win against the always-challenging Benoit Paire. Nadal lost despite outpointing Muller, 198-191.
Nadal, the reigning French Open champion, has not been to the Wimbledon quarterfinals since 2011. This defeat came against World No 26 Gilles Muller of Luxembourg who has been on the tour for 17 years and only this year won first of his two titles.
"It was not my best match but, at the same time, I played my best against a very uncomfortable opponent".
Otherwise, on the only day of the Grand Slam year on which all the men and women still alive in the draws participate, a slight upset hit the top in a women's game that brims with turbulence. The Djokovic-Mannarino fourth-rounder was postponed until Tuesday; it had been scheduled to be played on No. 1 Court after Nadal-Muller concluded.
The first two sets followed a similar pattern. Muller eventually pulled it out, 15-13. It's 30-40. Nadal is forced to the baseline and Muller opens it up to tuck the ball in the back corner. But the 15-time Slam champion came roaring back after looking dead in the water.
He broke for the first time at 3-1 in the third, unleashing a vicious inside-out forehand.
Nadal, ever the fighter, aced, and Muller netted his return for deuce, and Nadal went on to save his serve.
Still the players battled on until 28th game of a gruelling, but absorbing contest when Muller eked out a fifth match point.
Muller will now take on Marin Cilic in the quarterfinals.
Having won the first set, Muller, on serve, had the chance to level things up in the eighth game of the second set. The Swiss master has not even looked like dropping a set thus far, though Raonic picked up an impressive win over talented Alexander Zverev in round four that went the distance. He wish was granted.
The two-time Wimbledon champion clearly had his eyes on a third title despite his recent early exits from the championships.
Nadal has reacted and managed to stick it back to two sets anywhere thanks to its fighting spirit is legendary. Murray, bothered by a hip injury in the buildup to Wimbledon, was in Nadal's half. But imagine you're Grigor Dimitrov.
The 37-year-old Williams made her Grand Slam debut at the 1997 French Open, seven months before Konjuh was born.