Alcaraz was not at his best and got off to a rocky start in his second encounter in Rome, which Fabian Marozsan won 6-3, 7-6 (4).
Carlos Alcaraz was defeated 6-3, 7-6(4) by Hungarian qualifier Fabian Marozsan in the third round of the Italian Open on Monday, ending his quest for a third consecutive clay crown before the French Open.
The 20-year-old entered the competition after victories in Barcelona and Madrid, and he will replace Novak Djokovic as the world number one at Roland Garros, which begins later this month.
But Alcaraz was far from his best in his second encounter in Rome, dropping service to love in the fourth game as world number 135 Marozsan established a substantial lead and controlled the late exchanges to easily take the first set.
After saving three breakpoints earlier in the second set, Marozsan broke for a 4-3 lead, but the 23-year-old Budapest native quickly let his opponent off the hook before forcing a tiebreak.
Alcaraz raced out to a 4-1 lead, but Marozsan responded spectacularly, reeling off six points to inflict the world number two his only defeat on clay in 22 matches this season.
"It's not easy to say something," Marozsan stated shortly after his career-defining victory. "I'm overjoyed; I could never have imagined this." It was my dream the night before.
"I told myself that I'd try to do something special by winning a few games and maybe a set, and I just beat the (soon-to-be) world number one, the best player in our sport right now."
"Everything was perfect today."
It was Alcaraz's first loss to a player ranked below the top 100 since the 2021 Paris Masters, when he was defeated by Hugo Gaston.
World number three Daniil Medvedev defeated Spain's Bernabe Zapata Miralles 3-6, 6-1, 6-3 to reach the last 16 for the first time in Rome.
"I'm definitely playing my best tennis on clay right now," said Medvedev, who has reached the quarterfinals in both Monte Carlo and Madrid.
"I've never played better in Rome or Madrid." "I'm feeling fantastic."
Andrey Rublev, the sixth seed, also progressed after overcoming Spaniard Alejandro Davidovich Fokina 7-6(8), 6-3.
Elena Rybakina defeated Marketa Vondrousova 6-3, 6-3 in the women's draw to reach her first claycourt WTA 1000 quarterfinal, where she will play either top-ranked Iga Swiatek, the reigning champion, or Croatia's Donna Vekic.
Zheng Qinwen advanced to the quarterfinals after defeating Chinese compatriot Wang Xiyu 6-4 3-6 6-1, while American Madison Keys was defeated by Ukraine's Anhelina Kalinina 2-6 6-2 6-4.
Rain forced the suspension of Stefanos Tsitsipas' match against Lorenzo Sonego and Alexander Zverev's match against J.J. Wolf, which will be completed on Tuesday.
Tsitsipas won the opening set 6-3 against Sonego, while Zverev leads Wolf 6-4, 3-3.
Carlos Alcaraz Defeated By Fabian Marozsan In Italian Open 2023