Coco Gauff had seen enough.

During the No. 6-ranked American’s first-round 3-6, 6-2, 6-4 win against Laura Siegemund at the U.S. Open Sunday evening, Gauff blasted the chair umpire for not enforcing time violation rules for her opponent.

As Gauff held a commanding 3-0 lead in the deciding third set, she grew frustrated when Siegemund put her arms up to signal she wasn’t ready for Gauff’s serve and the umpire honored her request.

“She’s never ready when I’m serving, She went over to talk like four times, and you only gave her a time violation once, How is this fair?” Gauff said incredulously.

“No, you’re calling the score after the point is over, it’s not like we’re playing long points. You’re calling the score like six seconds after the point is over!”

“She’s 100 percent right,” ESPN commentator Patrick McEnroe chimed in.

“You have missed her like four times. She’s never ready! It’s not like we’re having, like 30-ball rallies. It’s two balls…I’m going at a normal speed! Ask any ref here, I go at a medium-pace speed,” Gauff continued.

“She can’t [go back] every single point. And everybody in this crowd knows I’ve been quiet this whole match…That first set was like every point. I didn’t say anything, but now it’s ridiculous. I don’t care what she’s putting on her serves, on my serves she has to be ready.”

The crowd roared in approval as Gauff returned to her post behind the baseline.

Siegemund, the No. 123-ranked player from Germany, had consistently been using up all of her time when she served and even earned a time violation warning during the third set.

Gauff dropped the first set 3-6 but bounced back to take the second set 6-2, and took command of the third set when she earned a couple of early breaks.

The American enters this tournament as one of the country’s best hopes for a Grand Slam, having won hardcourt tournaments in both Washington D.C. and Cincinnati this summer in the lead-up to the U.S. Open.