World number one Carlos Alcaraz says the stress of playing 22-time major champion Novak Djokovic led to the full body cramps which ruined his chances of winning their French Open semi-final.
Spain's Alcaraz, 20, started cramping early in the third set before Serbia's Djokovic, 36, won 6-3 5-7 6-1 6-1.
"It is not easy to play against Novak, he is a legend of our sport," he said.
"It has been really tough for me. I have never felt tension like I did in that match."
Top seed Alcaraz was only playing Djokovic for the second time and it was their first meeting at one of the four Grand Slams.
"If someone says he goes onto the court with no nerves playing against Novak, he lies," added the US Open champion, who will be replaced as world number one by Djokovic if he beats Casper Ruud in Sunday's final.
"The tension of the match was why the cramping happened. I started the match really nervous."
Djokovic, who said he had faced the same experiences when he was younger, added: "It is part of the learning curve. It is part of the experience.
"He's only 20, he's got plenty of time. He has showed so much maturity in the last couple of years.
"His career will be very successful if he manages to keep healthy because the game is there."
- 'I would have felt sorry about myself if I'd quit'
Alcaraz won his first Grand Slam title in New York last year, but this was only his second major semi-final and he faced an opponent playing in his 45th.
Alcaraz was out-of-sorts in a first set where he looked anxious in his shot-making and his body language, while Djokovic used all of his experience and know-how to move in front.
The Spaniard improved in what was another lengthy set, levelling what was turning into a classic contest even though the cramps had already started.
Djokovic took a medical time-out for an arm problem in the second set, taking a six-minute break before the third set while Alcaraz remained on court.
Shortly after, the seriousness of the physical issues for the Spaniard soon became even clearer.
After hitting a return into the net at 40-30 on Djokovic's serve in the second game, Alcaraz immediately pulled up and limped back to his chair to receive treatment.
"I would say the first set and the second set was really, really intense and I started to cramp in my arm," he said.
"At the beginning of the third set I started to cramp every part of my body, not only the legs. The arms, as well, every part of the legs.
"It was really tough for me to move at the third set, and in the fourth set let's say I had a little chance, but it was really tough.
"My full body started to cramp."
Alcaraz twice received treatment on court, also taking a lengthy bathroom break at the end of the third set, but insisted quitting the match never crossed his mind.
"I would have felt sorry about myself if I retired. I'm in a semi-final of a Grand Slam. If I retired from that, it could have been really tough for me," said Alcaraz.
"Thinking about the fourth set, I thought that probably I have 1% chance to come back.
"In the fourth set I had break points in the first game and after that, I just continued playing. I was not thinking about retirement."