With her struggles and her litigation, Bouchard acknowledged that she, too, was surprised by her court assignment.

“I was surprised, yeah,” Bouchard said. “But it’s always an amazing opportunity to play on the biggest tennis court in the world.” — BEN ROTHENBERG

Mladenovic’s Struggles Continue

Kristina Mladenovic, the No. 14 seed, was the first seeded player to lose on Wednesday, falling to Monica Niculescu, 6-3, 6-2, in a first-round match that began Tuesday.

Mladenovic had been one of the most dominant players early in the season. From February through the fourth round of the French Open, she compiled a 31-8 record, which included a title in St. Petersburg; finals in Acapulco, Stuttgart and Madrid; and a semifinal in Indian Wells.

But after an electrifying win in the fourth round of the French Open over the defending champion Garbiñe Muguruza, Mladenovic has stalled, going 7-10 and losing her last five matches, all in straight sets.

Mladenovic in May was ranked as high as fourth in the year-to-date rankings, which determine the field for the year-ending WTA Finals in Singapore. She is currently ninth in that race, one spot out of the top-eight cutoff. She is likely to fall further after this U.S. Open. — BEN ROTHENBERG