The Bulgarian seventh seed slumped to a 7-5 7-6 7-5 in an error-strewn display as his French opponent raced through to a quarter-final showdown with Roger Federer at Flushing Meadows.
And Dimitrov, 23, was not happy with his all-round performance in New York against the 20th seed.
“It was a very poor match for me,” said Dimitrov. “I don’t know. Where should I begin? Just a bad match for me.
“I didn’t play as close to the way I wanted to, and I think it was a great stage for me to come out on there on the centre court and perform my best.
“Everything went the opposite way today. I don’t have to be too down for that. Of course I have to give credit to Gaël that he played a really good match, but I also did a lot of unforced errors and that cost a lot. 6-3 in the tiebreak, I had all odds on me. And it was just poor shot selection. Eventually I didn’t execute at the right time.”
Meanwhile, Monfils is set to face Federer again after they met last month in Cincinnati, when the Swiss won in three sets en route to the title.
Asked about his match-up with Federer, Monfils said: “He’s definitely the legend of the tennis.
“I think right now he’s the greatest tennis player we ever had, and for me it’s always challenging to play against him.
“It’s always great, because no matter what I will say to my children, I played against him.
“I play tennis to play against a big legend, big court, show time. That’s what I train for. That’s why every day I wake up and I wish I could play those matches.
“For me, the best thing that can happen is to play against that guy on that stage.”
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