Indian Wells, United States: Former world number one Garbine Muguruza out-lasted seventh-ranked Kiki Bertens 5-7, 6-1, 6-4 Tuesday to reach the WTA quarter-finals at Indian Wells.
Spain's Muguruza, a two-time Grand Slam champion who has slipped to 20th in the world, said mental strength was the key in her 2 hour, 26 minute battle against Bertens.
After an exchange of breaks in the third set, Muguruza finally finished it off with a break of Bertens in the final game, a last bruising rally ending when Bertens spun a backhand wide.
"I don't think it was about the game, it was about staying strong mentally," Muguruza said. "I never gave up on one point.
Trailing 5-3 in the opening set, Bertens finished off a service hold with three service winners, reeling off four straight games to pocket the set after 71 minutes.
Muguruza had a chance to serve it out at 5-4 but never led in the game, and after Bertens held for 6-5 it was the Spaniard serving to save it. She fended off a pair of break points before smacking a volley into the net on Bertens' third set point.
But after Bertens won the first game of the second set it was all Muguruza as she won six straight games to force the third.
Muguruza next faces 18-year-old Canadian Bianca Andreescu, who surprised China's 18th-seeded Wang Qiang 7-5, 6-2.
Andreescu, who roared to her first WTA final as a qualifier in Auckland in January -- beating two former world number ones on the way -- is in the quarter-finals of one of the WTA's elite premier mandatory events for the first time.
Andreescu improved her match record for 2019 to 25-3, including qualifying as she became the youngest player to make the last eight at Indian Wells since a 17-year-old Anastasia Pavlyuchenkova reached the semis in 2009.