NEW YORK — Her match over, Serena Williams threw on a white T-shirt and moved almost directly to an outside practice court with her coach. A news conference and other niceties could wait. A crowd formed in the little grandstand by the far practice court, bigger than those at some of the actual U.S. Open playing courts as Williams worked on serves, especially second serves.

“Just trying to get those second serves in,” Williams said later of what was on her mind inside Arthur Ashe Stadium.

During the first set of the second round Wednesday, her second serves kept turning into double faults. Kiki Bertens of the Netherlands had grabbed a quick lead and stayed relaxed. Williams was back on the high wire where she has spent so much of the early rounds of this year’s Grand Slams.

Williams survived, 7-6 (7-5), 6-3, after falling behind a break, getting it back, and then dropping the first four points of the first-set tiebreaker.

“When I get down, I tend to get really relaxed and I start to play better,” Williams said.

Meanwhile, her sister, Venus, moved closer to the tournament’s second week by beating Irina Falconi 6-3, 6-7 (2), 6-2 in an all-American second-round matchup.

Venus got to the semifinals at New York five years ago. Since then, she has lost in the first round once, the second round twice and the third round last year.

The 23rd-seeded Williams could face younger sister Serena in the quarterfinals.

In other action, Belinda Bencic of Switzerland played through the tears to rally from the brink of defeat.

After crying during a changeover and repeatedly arguing with the chair umpire, the Swiss teen faced triple match point in the second set before coming back to beat Misaki Doi 5-7, 7-6 (3), 6-3.

Also, Eugenie Bouchard has a winning streak for the first time in nearly six months.

Bouchard, the 2014 Wimbledon runner-up, has been going through a rough season, and her 6-3, 6-7 (2), 6-3 victory over Polona Hercog of Slovenia represented the first time since March that she won twice in a row.

In men’s play, Rafael Nadal won the 22nd of his last 23 U.S. Open matches to advance to the third round, defeating Argentina’s Diego Schwartzman, 7-6 (5), 6-3, 7-5, on the Louis Armstrong court.

Milos Raonic, a 10th-seeded Canadian, needed massage treatment in each of the last three sets of his 6-2, 6-4, 6-7 (5), 7-6 (1) win over Fernando Verdasco.

In the day’s final second-round match, No. 1 Novak Djokovic of Serbia took a bit of time to get going, splitting the opening eight games, before reeling off 14 of the remaining 17 in a 6-4, 6-1, 6-2 victory over 52nd-ranked Andreas Haider-Maurer of Austria.

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