Fifth-ranked Petra Kvitova, 13th seed Kiki Bertens and Naomi Osaka, the No 20 seed, all progress
Wozniacki and top seeds safely through to US Open second round
A host of top female seeds, led by world No 2 Caroline Wozniacki, safely booked their places in the second round of the US Open on Tuesday.
In stark contrast to world No 1 Simona Halep's stunning defeat on the first day in New York, it was smooth-sailing for second seed Wozniacki, fifth-ranked Petra Kvitova, 13th seed Kiki Bertens and Naomi Osaka, the No 20 seed.
Latvian 10th seed Jelena Ostapenko also progressed, but the 2017 French Open champion was forced to dig deep in her opening encounter.
Wozniacki, who clinched her first grand slam title at the Australian Open in January, struggled for form on the American hard courts in the lead-up to the final major of the season, losing her opening matches in both Montreal and Cincinnati.
But the 28-year-old Dane was far too good for 2011 US Open champion Samantha Stosur, defeating the Australian 6-3, 6-2 in one hour and 24 minutes.
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"It's definitely difficult, it's very hot out here today," Wozniacki said. "I just tried to cool down between games, used ice."
Wozniacki next faces Ukrainian Lesia Tsurenko, a 6-3, 6-2 winner over Belgian Alison Van Uytvanck.
"She's a tricky opponent, great backhand," said Wozniacki, who will be aiming for third time lucky in New York after twice being a losing finalist, in 2009 and 2014. .
"I'm just glad to have won this one. When I saw I was playing Sam I knew it wasn't going to be easy."
Kvitova was equally untroubled in her first-round assignment after the fifth seed from the Czech Republic dispatched Yanina Wickmayer 6-1, 6-4 in one hour and 12 minutes.
Two-time Wimbledon champion Kvitova, who has never progressed beyond the quarter-finals at the US Open, will take on China's Yafan Wang in the second round after the world No 90 defeated Slovakia's Anna Karolina Schmiedlova 6-1, 3-6, 6-4.
Indian Wells champion Osaka joined Wozniacki and Kvitova with a straightforward win of her own, with a 6-3, 6-2 victory over Germany's Laura Siegemund in one hour and 18 minutes.
Osaka, the No 20 seed from Japan, will face Julia Glushko after the world No 162 fought back to claim a surprise 3-6, 7-5, 6-4 win over 62nd-ranked Monica Niculescu from Romania.
Bertens, considered a leading contender in New York following her title triumph in Cincinnati, sent out an ominous warning to her rivals with a 6-0, 7-5 win over Kristyna Pliskova of the Czech Republic.
While many of the top female players enjoyed easy outings, Ostapenko was forced to win the hard way, edging past Germany's Andrea Petkovic 6-4, 4-6, 7-5 in two hours and 18 minutes.
Ostapenko, 21, looked to be cruising when she led by a set and 3-1, only to be twice broken to allow Petkovic to level the match.
Once again, the Latvian seized control in the deciding set but squandered two match points when serving at 5-4, allowing Petkovic to break once again.
However, Ostapenko ramped up the pressure with Petkovic serving at 5-6, and the 10th seed claimed the match on her fourth opportunity.
Taylor Townsend is next up for Ostapenko after the American defeated compatriot Amanda Anisimova 3-6, 6-4, 6-3.