-- NEW YORK -- In the midst of a seriously scratchy game that featured four double faults, Serena Williams gave herself some stellar coaching advice.
"Please find your serve," she pleaded.
Williams, who by consensus owns the best serve the women's game has ever seen, has made a fine living -- sometimes routine -- winning while playing less than her best.
With the continuing weight of history on her broad shoulders, she survived and advanced yet again, defeating Dutch qualifier Kiki Bertens 7-6 (5), 6-3.
Not only did Williams win that erratic and monumental 11th game of the first set, in a microcosm of the wild tiebreaker that followed (and the season at large), she came back from a 4-0 deficit to win seven of the last eight points.
So the quest for the elusive calendar-year Grand Slam lives for another day -- Friday, to be precise, with a third-round match against fellow American Bethanie Mattek-Sands.
"I've been really relaxed," Williams said in her on-court interview. "Today I was tight. It definitely doesn't worry me being down a lot. I know I can try to make a comeback. Plus, I never stop giving the best effort that I can."
Williams has now won:
? 23 consecutive major singles matches in 2015.
? 30 straight in Grand Slams, going back to last year's US Open.
? 23 consecutive matches at the US Open, where she is the three-time defending champion.
Williams' encounter Wednesday was something a little different from her first-round win against Russian Vitalia Diatchenko, who retired with an ankle injury after trailing 6-0, 2-0. In that match, Williams won 32 of 37 points and walked of the court after 30 minutes.
Against the fearless and hard-hitting Bertens, Williams needed 92 minutes to shut it down and lost nine games and 65 points in the process.
To get there, the 110th-ranked Bertens had to win three qualifying matches and a three-setter in the first round of the main draw against Mirjana Lucic-Baroni, who made the fourth round here a year ago.
Bertens, 23, broke Williams in the match's third game with a superb running forehand pass and made it hold up for the longest time. But serving for the set at 5-4, she threw in three forehand errors and a double fault to bring Williams back even.
Bertens, who came in with a losing record this year and has never beaten a top-10 player, ran off to a 4-0 lead in the tiebreaker. But she couldn't withstand the pressure of Williams -- or the moment, for that matter.
Maybe Williams needs a slow start to kick-start her game. Perhaps she needs to make things interesting to summon her fierce powers of concentration. Whatever the reason, she has played fast and sloppy this Grand Slam season. She has lost a total of nine sets in majors this year, seven of them the opening set.
Tellingly, she looked a little subdued during her victory twirl at Arthur Ashe Stadium. Williams knows she's going to have to serve better when she meets Mattek-Sands and going forward, perhaps Madison Keys in the fourth round and Belinda Bencic in the quarterfinals.
Williams has now amassed 50 wins against only two losses this season.
"That's a lot," she said, sounding impressed. "I enjoy playing tennis. I enjoy the fact that I'm 33 years old and doing good."