The American third seed seemed to struggle physically in high temperatures in New York, with the extreme heat policy again in place.

Stephens hit 27 unforced errors and lost 6-2 6-3 on Arthur Ashe Stadium.

Sevastova will face Serena Williams in the first Grand Slam semi-final of her career on Thursday.

 

If you were defending, you'd be playing the same exact people all over again, which I didn't

Sloane Stephens

The high temperatures have been a significant issue during this year's championships with the conditions described as "dangerous" in the opening rounds.

"I think it was very physical today and tough to play," Sevastova said.

"It was so hot in the stadium. I just kept fighting."

Stephens struggled with her movement, was repeatedly being caught out by Sevastova's drop shot and after a number of wayward errors was bent double on the court.

She failed to put up a fight in a one-way first set and soon fell 4-1 behind in the second.

Encouraged by her home crowd, the world number three threatened a comeback by getting the match back on serve at 4-3 but was then broken again before Sevastova served out.

'I thought maybe I'd make the top 100'

Sevastova lost to Stephens at last year's US Open

The career-best Grand Slam performance for Sevastova comes after she retired from the sport in 2013 because of recurring injuries only to return in 2015.

The 28-year-old was appearing in her third Grand Slam quarter-final - the previous two also coming at the US Open in 2016 and 2017 - and admitted she was not expecting to hit such heights on her return to the sport.

"I did not have many goals," said the Latvian. "Maybe the top 100.

"But now, obviously when you win more you have higher goals. And when you're winning a tournament, you think that's normal."

Stephens said that despite the manner of her defeat on Tuesday she was content with what she had achieved at this tournament.

"The fact that I made it to the quarter-finals, played some really good matches and I competed as hard as I could, means I have a lot to be proud of.

"Defending a title is very hard, very difficult. If you were defending, you'd be playing the same exact people all over again, which I didn't.

"I'm not going to dwell on it. Just keep building. There's four more tournaments left. I'm just going to try to play the rest of the season as hard as I can and hopefully have some more good results."