Kyle Edmund refused to blame a knee problem for his collapse against Fernando Verdasco and instead admitted he is not fit enough.
The British No.1 looked to be on his way to the third round at Wimbledon for the second straight year when he led his veteran Spanish opponent by two sets and 3-0, but he let Verdasco back in and then appeared to hurt himself in a slip on the baseline.
Edmund has had a difficult season, with a left knee problem dogging him since last October, but he received treatment to his right knee here as well as his back at consecutive changes of ends, speaking to both the doctor and the trainer.
Edmund's movement was certainly compromised and his resistance ran out as Verdasco wrapped up a 4-6 4-6 7-6 (3) 6-3 6-4 victory to book a third-round date with Italian Thomas Fabbiano.
But Edmund played down the impact of the slip in the eighth game of the third set, saying: "I think my leg just straightened. In that moment, I felt something. I was able to play on from that.
"It didn't hold me back at all. I physically was not able to keep going with the power and reaction and stuff. I need to improve physically for next time I step on court.
"Being able to play three and a half, four hours, you need to put the work in. It doesn't just happen.
"At the same time, I'm still up in the match, and the 3-1 game cost me. That was my fault."
The turning point came in the fifth game of the third set, with Verdasco looking like he knew his time was up.
Edmund led 40-0 only to lose the game with five unforced errors, giving Verdasco a reason to believe again and changing the momentum of the match.
It is the second time Edmund has lost from a winning position against 35-year-old Verdasco in two months having also slumped to defeat from a set and 4-1 up on clay in Rome.
When told that John McEnroe had accused Edmund of blowing it, the 24-year-old said: "That's his opinion. I'm obviously disappointed. There will be for sure a lot of people saying that."
Edmund has only won eight tour-level matches this season compared to 24 at the same stage 12 months ago, but he denied the issue is mental as well as physical.
"I'm a good tennis player," he said. "You don't lose that match from not having enough tennis matches, in my opinion."
The good news for Edmund was that his left knee held up okay and he remains hopeful of finishing the season strongly.
He will concentrate on training before returning to action at the Citi Open in Washington at the end of July.
"The tennis season is so long," he said. "This time last year, I got ill straight after Wimbledon, won two matches in the US hard court series, I think (he actually won three).
"I literally have nothing to defend there. There's a great opportunity there.
"It would be nice to go in there feeling really good, having a good run of matches. For sure there is stuff to play for."
Novak Djokovic sailed smoothly into the third round of Wimbledon after a trouble-free straight-sets win over Denis Kudla.
The reigning champion's defence of his title was never threatened by the American and he strolled to a 6-3 6-2 6-2 win on Centre Court.
Djokovic, going for a fifth Wimbledon crown, will undoubtedly face sterner tests ahead but maybe not until the semi-finals after the draw has opened up favourably for him.
He faces Hubert Hurkacz in the next round - a Polish player who is enjoying his best ever Grand Slam run.
The writing was on the wall for Kudla when Djokovic won the opening five games, though a mini-fightback did at least delay the Serbian racing to the first set.
Djokovic barely had to get out of second gear and broke Kudla's serve regularly to set up the easiest of wins in 93 minutes.