She said Stephens' shots take time away from opponents.
However the intense heat that has plagued this year's tournament continued on Arthur Ashe on Tuesday and Stephens suffered.
It was only the fourth time in 282 career Grand Slam matches that Nadal lost a set by a 6-0 score. "I played some good ones before, but not that long, not that long against the great guys on the Grand Slam stage". It just was a really tough day. The defeats of Stephens and Pliskova completed the exodus of top 10 seeds.
She and Pliskova have history at Flushing Meadows. The 20-year-old became the first Japanese woman in the US Open last-eight since Shinobu Asagoe in 2004.
It was too much of the match played in the shadows of an afternoon on court which reaked havoc on the two players.
Stephens looked like she might have gained a foothold when she broke back for 2-1 at the start of the second set, letting out a scream of defiance, only for Sevastova to win the next two games. The petite Latvian was seen constantly frowning and mumbling to her box.
Sloane Stephens, of the United States, reaches for a shot from Elise Mertens, of Belgium, during the fourth round of the U.S. Open tennis tournament Sunday, Sept. 2, 2018, in NY.
"I think it was very physical today". Also good serve and moving well.
Colin Kaepernick Nike Advert 'Fixed' By Donald Trump Jr
Watch Hannity's mini-monologue above, plus Tomi Lahren asking Californians what they think about Nike's Kaepernick ad campaign. Now Nike is also losing the trust of many fans - and the company is watching as potential customers rush to other companies.
Judge Kavanaugh vows to be a ‘neutral and impartial arbiter’
Kavanaugh has produced more records to the committee than any other Supreme Court nominee in history, according to the chairman. That court is believed to be the second most important court in the country, after the Supreme Court .
Brazil's Lula banned from presidential race
He also accused political opponents of convicting him without evidence in an attempt to take him out of the election . Former Brazilian President Luiz Inacio Lula da Silva speaks during a rally in Curitiba, Brazil, March 28, 2018.
"Focusing on those little things definitely helped me in the earlier rounds".
No. 3 Stephens mixed her consistent, defense-to-offense style with the occasionally spectacular shot.
Stephens, 25, put pressure on her opponent's serve throughout the first set, but failed to convert any of the seven break points in her favor.
"I'm going to remember this match forever, for sure", said a dejected Thiem. "I need to play my best match of the tournament if I want to keep having chances to stay in the tournament".
It was Stephens' less-heralded Latvian opponent who has been taking her opportunities in NY.
A powerful forehand emerged from the shaded end of the court as Stephens converted a break point for the first time in the match, followed by a determined roar.
Peter Bodo has been covering tennis for over 35 years, mostly recently for ESPN. But having returned to tennis in 2015, Sevastova has risen steadily through the ranks and is now ranked No 18 in the world. Right now you're in the tournament, you're playing next tournament next week, and you don't feel it.
Stephens went on a shocking run after her victory on home soil a year ago, and, with no wins to defend for the remainder of the season, she's relishing the opportunity to add to her rankings total. "I can win it maybe next week again". It's cruel sometimes tennis, because I think this match didn't really deserve a loser.