Australian top seed Daria Gavrilova has booked her place in the quarter-finals of the San Antonio Open.

Gavrilova downed Greek Maria Sakkari 4-6 7-6 (7-5) 6-3 in just over two and a half hours and next faces Alison Riske for a spot in the semis after the American upset Belgian seventh seed Kirsten Flipkens 7-5 6-1.

Sixth-seed Misaki Doi is the second-highest seeded player left in the tournament after a 7-5 7-6 (7-4) win over Xinyun Han.