Sloane Stephens's US Open title defence ended with a 6-2, 6-3 quarterfinal defeat to Anastasija Sevastova on Tuesday as the Latvian avenged a 2017 loss to the American at the same stage.
Sevastova, through to the semifinals of a Grand Slam for the first time, will face either 23-time major champion Serena Williams or eighth-seeded Czech Karolina Pliskova for a place in the final after toppling Stephens in brutal heat and humidity on Arthur Ashe Stadium.
"I think it was very physical today. It’s tough to play, so hot in here. The first set was so important," said the 19th-seeded Sevastova, who broke Stephens in the final game to pocket the opening set.
She earned the last of five breaks in the second set to take a 5-3 lead and served it out on her third match point when a weary Stephens put a backhand into the net.
Anastasija Sevastova -- Cruises to the semi-finals
With the heat, humidity and blazing sun combining to make conditions hazardous enough that organisers suspended junior matches, the scraps of shade on the massive Ashe court were invaluable.
Stephens was ranked 83rd in the world when she upset Sevastova in three sets in the quarterfinals last year, trailing by a break in the third set before winning it in a tiebreaker.
Now No 3 in the world, Stephens joined an exodus of women's seeds that saw top-ranked Simona Halep and No 2 Caroline Wozniacki exit in the first two rounds.