Six-time champion Serena Williams battled through a challenging three-set test against Greek 15th seed Maria Sakkari to reach the US Open quarter-finals.
Williams, 38, looked composed as she took the first set in 37 minutes.
The third seed lost a close tie-break in the second and was forced to find her best tennis to come from a break down in the third and win 6-3 6-7 (6-8) 6-3 almost two hours later.
“I just kept fighting,” Williams said.
“She was doing so well. She was being so aggressive and I knew I needed to do the same thing.”
The American is seeking a 24th Grand Slam singles title as she attempts to equal Margaret Court’s record.
Her next opponent is Bulgaria’s Tsvetana Pironkova, who has never reached the US Open quarter-finals before and is playing her first tournament since Wimbledon 2017.
Pironkova beat French world number 56 Alize Cornet 6-4 6-7 (5-7) 6-3.
American second seed Sofia Kenin, the 2020 Australian Open winner, lost 6-3 6-3 to Elise Mertens of Belgium.
Mertens, seeded 16th, will face Victoria Azarenka of Belarus in the last eight after the former world number one reached her first Grand Slam quarter-final in more than four years.
The 31-year-old fought back from a set down to beat Czech 20th seed Karolina Muchova 5-7 6-1 6-4.