Gibbs, the world No 127, had to qualify to make the main draw here, but the 24-year-old American troubled Pliskova with her aggressive ball-striking from the baseline.
She arrived in NY having a rough season, failing to qualify at any of her past three events.
"Last Grand Slam of the season and knowing you played fine previous year, you just want to play that good again", Pliskova said. She joins No. 2 Simona Halep, No. 5 Caroline Wozniacki, No. 6 Angelique Kerber and No. 7 Johanna Konta.
Here are five things to watch out for on day six of the U.S. Open on Saturday.
No. 20-seeded Vandeweghe, who reached the semis of the Australian and quarters of Wimbledon this year, outlasted 10th-seeded Agnieszka Radwanska 7-5, 4-6, 5-3 in just under 3 hours.
The Latvian progressed to the third round for the first time despite looking far from her best, with a 6-4 6-4 victory. No. 12 Pablo Carreno Busta is the top seed in the other, which will send a first-time Grand Slam finalist to Arthur Ashe Stadium for the championship match next Sunday.
Osaka needed three sets to beat Czech Denisa Allertova 6-3, 4-6, 7-5.
Pliskova advances to to the fourth round, where she'll face either unseeded American Jennifer Brady or unseeded Monica Niculescu.More news: Sri Lanka fail to gain direct entry for 2019 World Cup
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Consistency has been a challenge for Pliskova, who has managed to play well in the biggest moments of her matches at Flushing Meadows but has yet to put together a complete performance.
That lack of training and the resulting lack of timing - rather than pain from his back - is what Federer said caused him problems Tuesday night in the first round against 19-year-old American Frances Tiafoe and again against Youzhny, a former top-10 player who reached the 2006 and 2010 U.S. Open semifinals but is now ranked 101st.
The No. 1 seed from the Czech Republic rallied for a 2-6, 6-3, 6-4 victory over American Nicole Gibbs on Thursday to reach the third round.
Pliskova turned the match around after a slow start to avoid becoming the fifth player among the top seven seeds to be eliminated.
Svitolina played only 1:22 in her Thursday match as she dispatched Evgeniya Rodina of Russian Federation 6-4, 6-4.
A five-time title victor in 2017 after claiming the Rogers Cup three weeks ago, Svitolina reached the third round for the third consecutive year. She made it to the round of 16 at the Australian Open in January. She promptly broke back to finish off the victory in 56 minutes.
Ukrainian fourth seed Elina Svitolina moved into the round of 32, but eighth seed Svetlana Kuznetsova crashed out.