In a match played with the roof closed because of rain, the Polish player was broken when serving for the match at 5-1 but sealed the victory two games later.
“I think it was much tougher than the score says,” Swiatek said. “It was really intense physically. She didn’t give me many points for free.”
“It was tough, but I am happy that I was consistent in being proactive,” she added. “I’m pretty happy that I won and can play the next round.”
Pegula served for the match at 5-4 in the second but was broken, before regrouping to win the tiebreaker. She’ll next play Marta Kostyuk of Ukraine or Olivia Gadecki, a wild-card entry from Australia.
The left-handed Shnaider, who is scheduled to attend North Carolina State this fall, saved two match points on her own serve at 5-2 down. But Sakkari held from 0-30 in the next game.
“It was a very high level from both of us, I think she played an amazing match,” Sakkari said. “She’s very young; she’s very promising. Maybe she should consider not going to college and go pro.”
There will be no play on the outside courts until at least 3:30 p.m. local time because of rain.