NEW YORK — The have been a few speed bumps for Coco Gauff at the US Open, but Tuesday’s quarterfinal was not one of them. 

Facing an erratic Jelena Ostapenko in the noon heat at Arthur Ashe Stadium, the No. 6 seeded Gauff breezed into her first-ever semifinal here with a 6-0, 6-2 victory that was never in doubt over the course of 68 minutes. 

"Today was the best match I've played, for sure," said Gauff, who has won 16 of her last 17 matches including tournament titles in Washington, D.C. and Cincinnati. "My decision-making was probably the best I've had, and I feel really confident in all my strokes."

Whereas Ostapenko played phenomenally on Sunday night to take out No. 1 and defending champion Iga Swiatek, she could not put any similar stress on Gauff because she simply could not keep the ball in the court. 

With Gauff playing solid enough and looping the ball in high and without much pace, she baited Ostapenko into overhitting and got 36 unforced errors as a result.

Ostapenko, who beat Gauff at the Australian Open back in January, said she felt her chances were compromised from the quick turnaround of the Swiatek match, which concluded the Sunday session and finished after midnight.

"Today was not really good match from me," Ostapenko said. "I think it's really hard to recover from those night matches, because after beating world No. 1, I went to sleep at, like, 5:00 in the morning, and still, you sleep for, I don't know, maybe like seven, eight hours, but you don't completely recover. Yesterday the whole day I felt very low energy. I thought today I was, like, going to wake up and feel better. But honestly, I didn't really feel much better."

Gauff, the 19-year old from Florida whose stardom was cemented four years ago when she made the second week at Wimbledon, is now a significant favorite to reach her first US Open final. She will face the winner of the quarterfinal between No. 10 seed Karolina Muchova and No. 30 Sorana Cirstea, who play later Tuesday. Gauff beat Muchova fewer than three weeks ago in the Cincinnati finals, which stands as the biggest title of her career thus far.

"I'm just going to go out there and focus on my side of the court, as I've been doing the whole tournament," Gauff said.

This is only the second time Gauff has reached this stage of a Grand Slam. Last year, she reached the French Open finals before losing to Swiatek but said the process of continually getting into the second week of majors has helped her learn how to manage her energy and the tension that comes along with playing so many difficult matches. In this tournament alone, she has needed three sets to take out Caroline Wozniacki, Elise Mertens and Laura Siegemund. 

"Right now I feel emotionally fresh, which I think was the problem in the past in Grand Slams," Gauff said. "I would be emotionally drained. Obviously I'm physically fresh and emotionally fresh, and I think that just came from experience.

"I think this is one of the harder runs I've had to the quarterfinal stage. Obviously never got to semis (in New York), but I don't know, I just feel so fresh, to be honest. I don't know if it's because I've been tricking myself or maybe when this is over I'm going to hit a wall. But I'm really proud of how I'm able to get through these matches."

It was fairly clear from the beginning Tuesday that Ostapenko was not going to offer the same type of resistance as her prior opponents. A boom-or-bust type of player with big, powerful strokes, Ostapenko could not find her rhythm or her range at any point and seemed dejected after quickly falling behind 3-0. 

Still, Gauff said it was a nerve-wracking finish knowing that her game could catch fire at any moment. 

"Playing Jelena you know that 6-0 set quite literally means nothing," Gauff said. "That's tennis in general because there's two out of three. I feel like that means even more nothing against her. I won't lie, I am surprised by, not the result but how the match went today. I'm happy with how I was able to stay in it."