The Pole went onto win the titles at those events, three of her six trophies collected in 2022.
On Wednesday, she came through a mistake-plagued quarter-final which featured 13 breaks of serve and a combined 61 unforced errors.
"It means a lot to be in the semi-finals for the first time," said Swiatek.
Swiatek overcame giving up the first break of the match in the fifth game to reel off 16 of the next 18 points to claim the opening set in 38 minutes.
The pair exchanged three service breaks apiece in the first eight games in an untidy second set.
It was the French Open champion who carved out the seventh break on a net cord to give herself the opportunity to serve for the match.
Eighth-ranked Pegula roused herself to stay alive before a double fault on break point in the 11th game handed Swiatek a second opportunity to seal a spot in the semi-finals.
The top seed failed again as Pegula grabbed the 10th break to send the set into a tiebreak which the Pole dominated.
"I am very happy as I have worked very hard but have kept my expectations low," said the top seed.
Sabalenka reached the semi-finals for a second successive year, fired up by the lingering and bitter aftertaste of her Wimbledon ban.
Russian and Belarusian players, such as world number six Sabalenka, were prevented from competing at the All England Club due to the invasion of Ukraine.
The ban deprived Belarus's Sabalenka of the opportunity to improve on her semi-final run in 2021.
"They took away one opportunity from me, so I worked really hard for this one," said Sabalenka.
She admitted that she made a determined effort not to watch any of this year's grass-court Grand Slam as she trained in Miami during her enforced break from the sport.
'Just an athlete'
"I'm just an athlete and I have nothing to do with politics," she said.
"It was a tough time, especially when I was working out in the gym and there was Wimbledon playing on the TV.
"I always turned it off because I couldn't watch it."
Belarusian players were banned from Wimbledon because Belarus is a close ally of Russia and has allowed Moscow to use its territory to launch attacks into Ukraine.
The 24-year-old world number six Sabalenka fired seven aces and a total of 30 winners past Pliskova, the 2016 runner-up in New York, without facing a break point.
Sabalenka is making the most of her great escape in the second round in New York when she saved two match points against Kaia Kanepi having been a set and 1-5 down.
On Wednesday, she raced through the first set in just 28 minutes on the back of three service breaks.
The 30-year-old Pliskova managed just a single winner in the opener while serving up five double faults.
Czech world number 22 Pliskova saved two break points in the eighth game of the second set but was unable to halt Sabalenka's powerful drive to the last four.
"When she's playing the way she is, there are not many rallies where you can get in that better feeling. She was serving amazing," admitted Pliskova.