Carlos Alcaraz admitted he played "the worst match of his career" as he suffered a shock defeat to Gael Monfils in the Cincinnati Open on Friday.

The Spaniard started well, racing through the first set before rain delayed proceedings with the second set level at 6-6.

When play resumed 24 hours later, Monfils picked up where he left off, winning the tie-break and the final set, to book a place in the last 16 at Alcaraz's expense.

After struggling to find his footing, Alcaraz says he found it hard to adapt while playing on Centre Court.

"It was really, really tough for me. I felt like it was the worst match that I've ever played in my career. Couldn't play, honestly," Alcaraz said.

"I've been practising really well here in this tournament. The previous days, I was feeling great, hitting the ball clear, you know, moving well.

"Probably I felt like it was another sport playing on the Centre Court [than] on the other courts. The balls were faster on the Centre Court bounced much, much, more than other courts.

"I don't know how I felt like this way, but, honestly, I couldn't control myself. I couldn't be better. So, this match it was impossible to win, and that's all."

Alcaraz's frustration was clear to see as he smashed his racquet on the court four times midway through the third set.

"I felt sometimes that I wanted to break the racquet," Alcaraz added. "It never happened before, because I could control myself in those situations, in those feelings, and most of the time I could control myself, and it could go better in the matches or in the situation that I've been feeling before.

"[This time] I couldn't control myself because, as I said, I was feeling that I was not playing any kind of tennis. So, it was really frustrating for me.

"There is some point that I want to leave the court. I don't want to be on the court anymore.

"So, it was really hurtful moment for me, and that's it. I think some players or a lot of players during their careers and during some certain moments, they can't control themselves, and it was one of those moments for me."

Alcaraz will be chasing his third grand slam title of the year at the US Open, which starts on August 26 in New York.