Johanna Konta failed in her bid to reach the Wimbledon semi-finals after an error-strewn display in a straight-set defeat by Czech Barbora Strycova.
The British number one started strongly, racing to a 4-1 lead, before collapsing to lose 7-6 (7-5) 6-1.
Let down by her previously dominant serve, Konta could not find a way back as - like in June's French Open semis - she crumbled when expectation was high.
"I did my best, and my best today wasn't good enough," Konta, 28, said.
"Every decision I made, every thought process, every opportunity I gave myself, I have no regrets in doing."
Strycova, who has reached her maiden Grand Slam singles semi-final just days after saying this could be her last Wimbledon, will face 23-time Grand Slam champion Serena Williams next.
"I think this was one of the best matches I have played," the 33-year-old said.
Konta's game deserts her
Konta came into the match boasting an incredible record of having lost just three of her 47 service games at these championships.
Despite the fact she got an early break, the warning signs that her biggest weapon might not be firing properly were there in the opening game when she had to save a break point.
The errors began to creep in at 4-2 when she sent two forehands wide and wild backhand long to allow Strycova to get the break back.
It became a theme as Konta went on to produce 22 unforced errors in that opening set, with the Czech increasing in confidence as she gave Konta a lesson in effective drop shots to take it to a tie-break.
There Konta could not find a rhythm, sending a forehand into the net to hand the set to the world number world number 54.
Konta is well versed in losing opening sets and winning in a third - with a record of 13 wins from 15 three-setters this year - but this time an early break in the second put a comeback out of reach.
The game was up for the Briton when she went long with a backhand - summing up everything that was wrong with this performance.
"I couldn't quite find the level that I needed to make it difficult and challenging for the kind of player she is," said Konta, who had lost to Strycova in 2017 in Tokyo in their only other meeting.
"She's a very difficult player to play on this surface, and in general. She's a very good player. It's just unfortunate I couldn't quite find the level needed to come through."
Favourite tag seems to hamper Konta again
Konta had been hoping to emulate her 2017 feat of reaching the last four and getting closer to becoming the first British women's singles finalist since Virginia Wade won the title in 1977.
She has enjoyed a successful year, reaching the French Open semi-finals and two WTA finals on clay, before transferring her good form on to grass.
Her serve has been the key but against Strycova she won just 51% of her first-serve points.
In the previous two rounds she came past 2017 US Open champion Sloane Stephens and two-time Wimbledon champion Petra Kvitova in three sets with accomplished displays but against the unseeded Strycova - where the Briton was now favourite - her game fell apart.
Her mental strength has often been questioned and it will be once again, with this defeat echoing her Roland Garros semi-final loss to another unseeded Czech, Marketa Vondrousova.
Konta, who was bidding to reach a fourth Grand Slam semi-final, denied that the pressure of expectation had got to her and refused to blame tiredness from back-to-back three-set matches.
"I was obviously nervous going into the match. But good nerves, excitement, anticipation," she said. "I wouldn't say that had anything to do with the level that I played or any difficulty.
"I think it was a combination of just not finding my level, and her not giving me the opportunity to find my level more than anything."
Analysis
BBC tennis correspondent Russell Fuller
This was a clever, skilful and tactically astute performance by Barbora Strycova. At the age of 33, she seized the opportunity to reach a first Grand Slam semi-final magnificently.
Johanna Konta, though, was unable to play with anything like the freedom of earlier rounds.
Thirty four unforced errors in two sets tells its own story: Strycova's spins and relative lack of pace threw her out of kilter, but nerves and expectations also seemed to play a part.
Konta played brilliantly to win her other Wimbledon quarter-final against Simona Halep two years ago, and also her recent French Open quarter-final with Sloane Stephens.
But just as in her Roland Garros semi-final with Marketa Vondrousova, Konta was the favourite here - and unable to play to the level she is capable of.