It was the seventh consecutive victory for seventh seed Swiatek, who won the title in Cincinnati last year.
"It's not like I was super tired after Toronto," the Pole said after her 6-3 6-0 triumph on Sunday (Monday AEST), two days after arriving.
"I knew I just needed a little bit of rest. Usually one day before a tournament, I'm already in my match mode. But this time, I wanted to spend every hour possible just chilling."
Aryna Sabalenka, who has spent 95 consecutive weeks at No.1 dating back to October 21, 2024 got past Australian Talia Gibson 6-2 7-6 (7-2) to improve to 15-3 in Cincinnati since 2022.
After three breaks opened the match, Sabalenka, the 2024 champion, proved too powerful again on return in the seventh game, before serving it out.
World No.65 Gibson held strong for 5-5 in the second set, but both players were broken to take it to a tiebreaker and the 22-year-old from Perth succumbed to end the first contest between the pair in a little under two hours.
"She really played great tennis. Especially in the second set, it felt like she played more aggressive and put so much pressure on my last service game," Sabalenka said of the Aussie, who's expected to rise to world No.61 as she gears up for her second US Open main-draw campaign.
"I honestly don't know how I would've handled another set (if I had lost the second set)."
Coming off her loss to Swiatek in the Toronto decider, No.2-ranked Elena Rybakina beat American Taylor Townsend 6-3 6-4.
Rybakina, who reached the semi-finals last year in Cincinnati, is looking for her 14th hard-court title after winning the Australian Open in January.
Elsewhere, fourth seed Coco Gauff won in three sets, as did eighth-seeded Ukrainian Elina Svitolina, while fifth seed Mira Andreeva cruised to a 6-1 6-0 thumping.
The 10th, 13th, 20th, 22nd and 23rd seeds - Marta Kostyuk, Iva Jovic, Maddison Keys, Marie Bouzkova and Barbora Krejcikova - also progressed.
With AAP.
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