Swiatek has had a vice-like grip on top spot since inheriting it after Ash Barty's retirement in April 2022, but Australian Open champion Sabalenka has steadily chipped away at the deficit and can leapfrog her rival by winning in New York.
Swiatek has not been beaten before the quarter-finals of a tournament since January but the Pole appeared to be running out of steam ahead of the year's final Grand Slam.
"From my perspective, I would say my tank of fuel is pretty empty," she said after going out in the semi-finals at Montreal and Cincinnati.
"I'm not even going to regret a lot because I'm happy I'm going to have days off."
The French Open champion said she would try not to be hard on herself ahead of her US Open title defence.
"I know from my experience that being a defending champion isn't easy," Swiatek said. "I'm going to take it easy on myself and just try to do everything step by step."
Despite needing to recharge and refocus, Swiatek will still be heavily backed to retain her crown and secure a fifth Grand Slam title overall but Belarusian Sabalenka underlined her own hardcourt credentials with her breakthrough win in Melbourne.
She followed that up by making the semi-finals at the French Open and Wimbledon, where she could have taken the number one ranking for the first time.
Sabalenka also enjoyed success in the US earlier in the year with a run to the Indian Wells final where she crashed to fellow big-hitter Elena Rybakina, another top Flushing Meadows contender despite recent health and fitness worries.
The trio have won five of the last six Grand Slams, sparking talk of a 'Big Three' era in women's tennis, but the game has churned out several other threats for the US Open crown in the last few weeks.
WELL PRIMED
Marketa Vondrousova heads that list after the former Roland Garros runner-up broke her Grand Slam duck at Wimbledon, while Jessica Pegula and fellow American Coco Gauff are primed for deep runs after triumphs in Montreal and Cincinnati.
"I believe in just giving it your all," said former French Open runner-up Gauff, who beat Swiatek en route to winning her first WTA 1000 title.
"That's all you can do. I'm going to give it my all in the U.S. Open. If things go great, that's exciting. If not I go back and work hard and get ready for the next one.
"That's the mentality you have to have."
World number three Pegula also raised U.S. hopes of a first home-grown Flushing Meadows champion since Sloane Stephens in 2017 after she beat Swiatek during her run to the Montreal title.
Ons Jabeur will hope to overcome a foot problem she suffered last week as she continues her quest for a first Grand Slam singles crown. The Tunisian trailblazer lost in the 2022 New York final and has been runner-up at Wimbledon the last two years.
Former world number one Caroline Wozniacki, twice a beaten finalist at Flushing Meadows, is one of those to be awarded wild cards for the tournament. The Dane returned to competitive tennis earlier this month after more than three years away to start a family.
