Both players overcame their troubles on Friday to reach the fourth round and keep alive the chances of a third straight meeting on the final weekend.
World No.1 Sabalanka beat Kamilla Rakhimova 6-3 6-4. The top seed was pushed in a second set that lasted 54 minutes - a minute longer than her entire previous match.
"She played incredible tennis," Sabalenka said. "She really pushed me so hard in the second set and I love when they bring their best tennis because they really push me to improve."
Trying to become the first player to win three straight US Open titles since Serena Williams from 2012-14, Sabalenka will face American Taylor Townsend in the round of 16.
Sabalenka was serving in the third game of her match in Louis Armstrong Stadium when she tossed the ball but then let it fall to the court. She did the same thing on the next point, with something clearly bothering her.
She then approached the chair umpire to ask for help because she smelled marijuana.
"I was like, guys, you can do whatever, you can smoke whatever, you can relax as much as you can, but please, to not do it around the tennis courts," Sabalenka said, when asked what she was thinking at the time.
"It's a bit tricky to handle that smell while you're trying to compete at your best."
World No.3 Pegula fought back to beat 2021 runner-up Leylah Fernandez 1-6 6-4 6-3. Pegula, who lost to Sabalenka in the 2024 final and again last year in the semi-finals, had a dismal start in which she put only five of 16 first serves in during the first set.
Fernandez hadn't won a grand slam singles match this year until getting to New York and was trying to reach the fourth round at the U.S. Open for the first time since falling to Emma Raducanu in the final five years ago.
Pegula handled her easily in their only meeting this year but said Fernandez showed her different looks that gave her trouble.
"I didn't start off very well. It was tough," Pegula said. "I had to dig deep there in the second to turn that around, and it very well could have not turned around."
Pegula advanced to face Sorana Cirstea, the 36-year-old from Romania who is contemplating retirement after this season. She will have at least one more Grand Slam match after the No. 16 seed beat No. 19 Jasmine Paolini 6-3 6-3.
Townsend reached the round of 16 for the second straight year by knocking off No.15 seed Diana Shnaider 6-2 6-7 (7-3) 6-3 and seemed eager for the matchup with Sabalenka.
"I'm so excited. I feel like I thrive in these moments," the American said. "I'm built for these moments and so now is my time, I'm ready to take it. I'm ready to go."
No.7 seed Karolina Muchova, the Wimbledon runner-up, was ousted by No.26 Emma Navarro. Marta Kostyuk, the No.11 seed, also advanced.
