WATCH: Carlos Alcaraz smashes his racquet during Gael Monfils loss in Cincinnati

CINCINNATI (AP) —Carlos Alcaraz repeatedly smashed his racket on the court in a rare show of frustration on Friday, and the four-time Grand Slam winner fell to Gael Monfils 4-6, 7-6 (7-5), 6-4 at the Cincinnati Open.

In a match that was suspended by rain on Thursday night with the players in a second-set tiebreaker, the 37-year-old Monfils advanced by taking the last two sets from the second-seeded Alcaraz, who called the loss his "worst match."

"I felt like it was the worst match that I've ever played in my career," Alcaraz said. "I've been practicing really well. I was feeling great. But I couldn't play. I want to forget it and try to move on to New York."

Read More: Frustrated Carlos Alcaraz calls Cincinnati Open loss to Gaël Monfils "worst match I ever played"

Trailing 3-1 in the tiebreaker when the match was halted, Alcaraz was hoping for a reset when play resumed Friday. But, the No. 3 player in the ATP rankings wasn't able to control his emotions.

I felt like it was the worst match that I've ever played in my career. Alcaraz after R3 defeat in Cincinnati

"It never happened before because I could control those feelings," Alcaraz said. "Today I couldn't. I was feeling that I was not playing any kind of tennis. It was really frustrating for me. At some point, I didn't want to be on the court anymore."

Alcaraz was playing his first match since earning a silver medal at the Paris Olympics after losing to Novak Djokovic, who also beat him last year in the Cincinnati final.

Monfils was back on the court Friday afternoon against No. 15 seed Holger Rune, looking to become the oldest men's quarterfinalist in Cincinnati in the professional era

The US Open begins in New York on Aug. 26.

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In women's action, top-ranked Iga Swiatek advanced to the quarterfinals with a convincing 6-2, 6-2 win over Marta Kostyuk.

Swiatek bounced back with a more complete performance after losing a second-set tiebreak on Wednesday before outlasting France's Varvara Gracheva.

"Today, I just kept my intensity at a high level all the time," Swiatek said. "It didn't really matter to me what the score was, I just wanted to continue playing my game. I focused on myself."

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No. 3 Aryna Sabalenka also advanced with a 7-5, 6-2 victory over Elina Svitolina, but No. 5 Jasmine Paolini, the runner-up at the French Open and Wimbledon, lost to Mirra Andreeva 3-6, 6-3, 6-2.

Top men to advance included No. 1 Jannik Sinner, who got a walkover against Jordan Thompson on his 23rd birthday, No. 4 Alex Zverev and No. 6 Andrey Rublev.