Karolina Pliskova and Madison Keys came through their openers at the US Open as Angelique Kerber crashed out on a rainy day in New York.
Pliskova, the world number one and last year's runner-up, needed just 78 minutes to get past Magda Linette in the first round on Tuesday.
The Czech was beaten by Kerber in the 2016 final, but the German's title defence came to an early end as she was crushed by Naomi Osaka.
Only seven matches were completed in the women's draw after persistent rain, with Keys advancing during the night session on Arthur Ashe Stadium.
KERBER CRASHES OUT
A winner of two grand slams last year, Kerber failed to go beyond the fourth round of a major in 2017, her latest defeat a 6-3 6-1 humbling at the hands of Osaka.
Osaka, 19, hit 22 winners in her comfortable victory, while sixth seed Kerber's 23 unforced errors proved costly.
"I tried not to think how good she was while I was playing her," the Japanese teenager said.
"I just tried to focus on what I could do to win the match, if that makes sense."
JOB DONE FOR PLISKOVA, KEYS
Pliskova is set to be hard to beat at Flushing Meadows and the powerful Czech cruised past Linette 6-2 6-1.
During the night session, Keys had a few more problems, but the American 15th seed beat Elise Mertens 6-3 7-6 (8-6).
Earlier, French Open champion Jelena Ostapenko overcame Lara Arruabarrena 6-2 1-6 6-1.
MIXED DAY FOR SEEDS
It proved to be a mixed day for the seeds, with Lesia Tsurenko also exiting, but Barbora Strycova won through.
Tsurenko, the 28th seed, was well beaten by Yanina Wickmayer 6-3 6-1, while Strycova was too good for Misaki Doi 6-1 6-3.
Sorana Cirstea was the other player to advance, the Romanian beating Lesley Kerkhove 6-1 6-3.
In matches interrupted by rain, Elina Svitolina led Katerina Siniakova 6-0 6-6 (2-1), Andrea Petkovic trailed Jennifer Brady 6-4 3-4 and Kristina Mladenovic was down to Monica Niculescu 6-3 1-1.