Decoding Federer's puzzling, poor performances

“When it happens like this, back-to-back matches, it’s just a bit frustrating more than anything,” he said, “especially when the level is that low and there are that many errors, and the energy is not kind of there. But, yeah, I can only do better, which is a great thing moving forward.”

Maybe the rust on his game was to be expected, with Wednesday’s match being just his fourth since his loss in the Wimbledon final to Novak Djokovic.

But he said he would refrain from drastic changes and would have a light practice Thursday.

“So tomorrow is really just to make sure I get to feel the ball again in an environment where I have no pressure,” Federer said, adding that he has put in a lot of work since Wimbledon. “Every ball I play out there, you feel like some sort of a pressure not to miss it, having to make it, wanting to hit a winner, hitting a good serve.”

His next opponent will be the winner of the match between Daniel Evans and No. 25 Lucas Pouille, which was scheduled for an outside court and was one of 58 matches that were postponed to Thursday.

Federer knows that his ability to play Wednesday and avoid the rain delay gives him an advantage. But as he noted, it is one he has earned.

“I think this roof is more important when it comes to semis and finals than a day like today because they’re going to fall behind,” he said and added, “Here, I definitely profit from everything, I guess, that I did in the game and my ranking, to be put on center court on a day like this.”

The only day matches completed Wednesday were played in Ashe and Armstrong. Third-seeded Karolina Pliskova of the Czech Republic defeated Georgian qualifier Mariam Bolkvadze, 6-1, 6-4, in women’s singles, and No. 10 Madison Keys beat Lin Zhu of China, 6-4, 6-1. On the men’s side, No. 7 Kei Nishikori beat the American Bradley Klahn, 6-2, 4-6, 6-3, 7-5. In the first night match in Ashe, the top-seeded Djokovic required treatment on his injured left shoulder but battled through the pain to defeat Juan Ignacio Londero, 6-4, 7-6 (3), 6-1.

Williams, who had not lost in the second round at the U.S. Open since 2013, said she was encouraged by how she played against a top-flight opponent, and she indicated that she wanted to play in the coming months, when the tour shifts to Asia. Williams also said she wanted to play more mixed doubles and return to the U.S. Open.

“There’s not a lot that I haven’t done or come close to doing, which is exciting,” she said, adding: “Of course I love the challenge of playing tennis. It’s beautiful.”