Serena Williams fought through a very challenging three-set game to beat Maria Sakkari to reach the US Open quarter-finals.

The six-time world champion looked composed as she led in the first set. But a close tie in the second forced her to come from behind to win 6-3 6-7 (6-8) 6-3 in the third set 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 38-year-old will face Bulgaria’s Tsvetana Pironkova in the quarterfinals.

Pironkova who has never reached the US Open quarter-finals before and is playing her first tournament since Wimbledon 2017, beat French world number 56 Alize Cornet 6-4 6-7 (5-7) 6-3.

FrujuSports had reported that Williams is seeking a 24th Grand Slam singles title as she attempts to equal Margaret Court’s record.