Serena Williams, seeking her 24th career Grand Slam title to match Margaret Court's all-time record, routed Croatia's Petra Martic 6-3, 6-4 on Sunday to reach the US Open quarter-finals. The 37-year-old American, a six-time US Open champion, will play for a semi-final berth on Tuesday against China's 18th-seeded Wang Qiang, who upset French Open champion Ashleigh Barty, the second seed from Australia. Williams had an injury scare in the second set of the 92-minute triumph when her right ankle went out from under her as she ran to the net and stopped to hit a volley. She called for a medical timeout at the next break and had the ankle heavily taped.
"I just rolled it. I don't know why," Williams said. "I was volleying and it just went over. That was frustrating so I wanted to get it compressed really fast."
Eighth-seeded Williams, who has battled knee and back injuries this season, felt a mental setback when it happened but battled through to win.
"I've had a rough year with injuries," Williams said. "It was like, 'Oh my God. Not again. I'm finally walking."
Williams, who won her first Grand Slam title 20 years ago at the US Open, advanced to the last-eight at Flushing Meadows for the 16th time.
"Am I that old? That's the first thing I think about," Williams told the crowd at Arthur Ashe Stadium. "But I'm doing it for all of us."
Williams won two years to the day after giving birth to her daughter Olympia.
"She was in my arms by now," Williams said. "It was literally amazing and it was like the best day of my life."
Williams said her daughter watches her on television enough to realize it's her on the screen, when she doesn't mistake Serena's sister Venus for her mom.
"She sees me on TV and says 'Mama," Williams said. "Sometimes she sees Venus and she says 'Mama,' but that's ok because Venus and me share everything."
Williams has reached three Grand Slam finals as a mother, including last year's US Open and Wimbledon in July, but has yet to win a Slam title as a working mom.
"When I go to bed at 9 o'clock now I'm exhausted," she said, adding. "This is for all you working parents out there."