NEW YORK — The enormity of what is at stake for Serena Williams at the U.S. Open — the first true Grand Slam in tennis in more than a quarter of a century — hit her Wednesday.
That, she said, is why her play was so uneven in the second round at Flushing Meadows, despite facing a qualifier ranked only 110th.
And it's why, after the 10 double-faults, two dozen other unforced errors and an all-around sloppy first set, Williams got pointers from coach Patrick Mouratoglou and headed straight to a practice court to put in work, hoping to repair what plagued her during a 7-6 (5), 6-3 victory over Kiki Bertens of the Netherlands.
"Today, I was a little tight," Williams said. "I think it showed."
Sure did. She got broken early. She double-faulted four times — yes, four — in one game. She didn't manage to earn a break point against the strong-serving Bertens until the 10th game. Williams trailed 5-3 in the first set, finally broke for 5-all, but then needed to erase a 4-0 deficit in the tiebreaker.
All attributable, at least in part, to thinking about what she is trying to accomplish these two weeks.
"Until today, I was OK with it. I just got a little nervous today," the 33-year-old American said. "But I've been doing totally fine. I've been completely relaxed, chill. I've been really, really fine. So I'm going to get back into the place that I was, and I'll be fine again."
She has won the past four major titles, a streak that began at last year's U.S. Open, and 21 overall. If she can win five more matches at Flushing Meadows — starting in the third round against Bethanie Mattek-Sands in an all-U.S. matchup Friday — Williams would complete the first calendar-year Grand Slam in tennis since Steffi Graf in 1988.
Also on the line for Williams: A 22nd major singles championship would equal Graf for the most in the Open era, which began in 1968, and second-most in history behind Margaret Court's 24. Plus, Williams is trying to become the first woman since Chris Evert in 1975-78 to win four consecutive U.S. Opens.
"Right now, she's on a mission to get a record," said Mattek-Sands, a 30-year-old wild-card entry, "and I'm here, playing my game."
Up and down all afternoon in Arthur Ashe Stadium, the No. 1-seeded Williams had trouble finding her game against Bertens, who only once made it as far as the third round in 14 majors.
On one point, Williams hit a 125 mph ace. On the next, she double-faulted. On one, she smacked a swinging forehand volley winner, bringing Mouratoglou to his feet in the stands. On the next, she pushed nearly the same shot wide with Bertens out of position.
Perhaps Williams was a tad rusty. In the first round, Williams' opponent, Vitalia Diatchenko, hurt her left foot while running sprints before the match and could barely move. Williams won 32 of 37 points in that one, which lasted about a half-hour until Diatchenko stopped playing while down 6-0, 2-0.
"I was definitely a little colder," Williams said. "But ... that is no excuse."
Williams complained earlier this season about a sore right elbow, and in one of her only two losses in 52 matches this season, at Toronto in August, she double-faulted 12 times.
That defeat came against Swiss teen Belinda Bencic, who is seeded 12th in New York and could face Williams in the quarterfinals. First, though, Bencic will play Williams' older sister, Venus, in the third round after both pulled out three-set victories Wednesday night.
The 35-year-old Venus, the U.S. Open champion in 2000-01, got past Irina Falconi 6-3, 6-7 (2), 6-2, while the 18-year-old Bencic saved three match points, cried during a changeover and argued with the chair umpire en route to coming back to beat Misaki Doi 5-7, 7-6 (3), 6-3.
After Venus finished her match in Arthur Ashe Stadium, No. 1 Novak Djokovic split the first eight games against 52nd-ranked Andreas Haider-Maurer of Austria before running away with a 6-4, 6-1, 6-2 victory, then doing a towel-waving jig on court with a man brought out of the stands.
Serena Williams knows she wants to avoid the sort of poor beginning she had against Bertens.
"I have to start out strong if I want to stay in the tournament," the younger Williams said. "If not, I can go on vacation."
Mattek-Sands made it to the third round at Flushing Meadows for the first time in 13 appearances by beating another American, CoCo Vandeweghe, 6-2, 6-1.
"You know what? Thirty is the new 21," Mattek-Sands said.
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