Sloane Stephens won’t repeat as U.S. Open champion after upset loss to Anastasija Sevastova

American Sloane Stephens will not repeat as the U.S. Open women’s champion.

Her reign was ended Tuesday by Anastasija Sevastova of Latvia, whose versatile game and steadiness in clutch situations provided the foundation for a 6-2, 6-3 victory over a frustrated Stephens in the searing heat at Arthur Ashe Stadium.

Stephens, the No. 3 seed here, could not convert any of the seven break points she had against No. 19 Sevastova in the first set. Stephens got her first service break to close within 2-1 in the second set, but Sevastova broke back for a 3-1 lead while Stephens began to curse at herself on the court for her frequent mistakes.

However, Stephens began to win some points with her forehand and she broke Sevastova’s serve and trimmed the Latvian’s lead to 4-3. But Sevastova, who showed great pace and ingenuity, broke for a 5-3 lead on her second break point and held serve to win the match.

“Today was a bad day. I wish I could have played better. The better player won,” said Stephens, who said she had been dealing with a sinus infection but did not blame that for her loss. “When you don’t play the big points well, the match can get away.”

Sevastova became the first Latvian woman to reach the semifinals at the U.S. Open. She will face the winner of the quarterfinal match between Serena Williams and Karolina Pliskova, which was scheduled for Tuesday evening.

The heat and humidity have been major issues in this year’s Open, particularly at Arthur Ashe Stadium. No. 2 men’s seed Roger Federer said after his upset loss to world No. 55 John Millman late Monday that the lack of air circulation in the stadium had made it difficult to breathe, a common complaint.

Shortly after 1 p.m. EDT Tuesday, tournament officials halted play in the boys’ and girls’ singles and doubles. In a statement, they said the wet-bulb globe temperature (a measurement designed to estimate the effect of temperature, humidity and other factors on humans) had exceeded 89.6 degrees. An extreme-heat policy was in effect for the men’s and women’s singles matches, meaning the women were permitted to take a 10-minute break between the second and third sets of their matches, while the men were permitted to take a 10-minute break between the third and fourth sets of their matches.

Stephens was gracious in defeat and wished her opponent good luck.

“It was very physical today,” Sevastova said. “It was very important that I won the first set and kept fighting to the end. I showed some nerves at the end but that’s normal.”