World No. 1 Serena Williams overcame a close first set to sneak a 7-6 6-1 over fellow American Christina McHale to advance to the quarter-finals of the Italian Open in Rome on Thursday.

The first set witnessed a see-saw contest with both players breaking each other’s serve once, but Williams rode on her superior experience to pull off a hard-fought tie-breaker, 9-7.

The top-seeded Williams, however, was at her usual best in the second set. Carrying on the momentum, she bagged 91 percent of her first-serve points and held on to her serve on all occasions to eventually seal the set 6-1, and the match.

This is not the first time that Williams was troubled by McHale’s persistence. At the Miami Open earlier this year, the duo went neck-to-neck before the former prevailed in a tough three-setter.

Moving on to the last-eight stage, the American powerhouse has been scheduled to cross the swords with Russia’s Svetlana Kuznetsova, the No. 9 seed, who overcame Australian Daria Gavrilova 6-2 2-6 6-3.

3^rd seed Garbine Muguruza of Spain had a routine day in the office as she moved past Latvian journeywoman Jelena Ostapenko, winning 6-1 6-4 in the battle that lasted one hour and 18 minutes. She next faces 11^th seed Timea Bacsinszky, who beat Carla Suarez Navarro 7-5 5-7 6-2.