Serena Williams advanced to her 12th straight U.S. Open quarterfinal, beating Greek Maria Sakkari 6-3, 6-7 (6), 6-3 in the fourth round on Monday.
Next up: fellow mom Tsvetana Pironkova, a Bulgarian playing her first tournament in three years.
Williams, eyeing a record-tying 24th Grand Slam singles title, battled past Sakkari after having her serve broken in the first game of the third set. She broke Sakkari three games later, then did it again to go up 5-3 before serving it out.
Williams served a 124 mile-per-hour ace late in the third set, fastest of the tournament.