Coco Gauff needed to battle following a sizzling first set on Tuesday to complete a 6-1, 7-6 (7/3) victory over Ann Li to reach the fourth round of the ATP-WTA Cincinnati Masters.
The 2023 champion had it all her own way in the opening set against her 29th-ranked American compatriot, but it proved more difficult to close the match out in a tight second set.
After Gauff swept the first in 30 minutes, the pair exchanged early breaks in the second on the way to a tie-breaker.
Gauff sprinted to a 4-1 lead and closed out victory on her third match point.
"She played better in the second set and I missed a couple of break opportunities," Gauff said. "I tried to forget about those.
"It was hard to control the ball for both of us and it was my first time playing a day match on this centre court so I had to adjust to that."
Mirra Andreeva's French Open reigning champion status counted for little as the fifth seed struggled to close out a 6-1, 7-6 (7/5) victory over Janice Tjen.
The Indonesian challenger ranked 37 was bowled over in the first set but made Andreeva work to finally advance.
Tjen saved two match points as Andreeva served for the win leading 5-4 and another in the tie-breaker before putting a return wide.
"It was two completely different sets," Andreeva said. "In the first I was in command and she had unforced errors here and there.
"But in the second after a couple of games I started getting nervous, she made fewer mistakes.
"It turned into a match of mentality and physicality. It was not easy – I had a lot of opportunities to close it out earlier, but even like this I'm super happy."
Madison Keys, the 2019 winner, dispatched Katerina Siniakova 6-1, 6-3 as the American polished her record against the Czech to 3-0.
Eighth seed Elina Svitolina was forced to withdraw before her match against Wang Xiyu with an ankle injury.
"Unfortunately I tried my best to recover but the injury I sustained in Toronto and also pushed by the second round match, I didn't recover as I wish I could to get ready for my next round," the Ukrainian said in a statement.
"I've been advised by the doctors to take a little bit of time to rest and recover completely."