Jessica Pegula and Karolina Muchova booked their places in the US Open quarter-finals with stress-free straight sets wins at Flushing Meadows on Monday.
On the United States' Labor Day holiday, American Pegula was efficient yet again while scoring a 6-4, 6-2 victory over Russia's Diana Shnaider.
The victory set up a meeting with either top seed Iga Swiatek or Liudmila Samsonova, who play later on Monday.
Sixth-seed Pegula, who missed the French Open due to injury but triumphed at a US Open tune-up event in Canada last month, said her game is trending in the right direction as the pressure-packed second week of the Grand Slam gets underway.
"Today was the best I've felt off the ground so I want to keep working and bringing my best tennis for the later rounds," Pegula said.
"There's always a lot of pressure here but I like it. It's nice being an American here and getting all the support."
Muchova, who like Pegula has yet to drop a set at the tournament, hit 17 winners to upset Italian fifth seed Jasmine Paolini 6-3, 6-3.
The unseeded Czech appears to be fully recovered from the wrist surgery that had sidelined her for 10 months and will next face either Brazil's Beatriz Haddad Maia or the veteran Caroline Wozniacki for a place in the semis.
