Miami,

Venus Williams upended defending champion Johanna Konta 5-7 6-1 6-2 on Monday to reach the Miami Masters quarterfinals while a dominant Victoria Azarenka also advanced with a straightforward win over Agnieszka Radwanska.

Three-time champion Williams stormed back from an early deficit to cruise past the British 11th seed, who needed several bouts of treatment on her lower back throughout a match that lasted two hours and 19 minutes.

Perhaps more impressive was that Williams, who turns 38 in June, was able to look so in control despite playing a day after spending nearly three hours on the court for her third round clash against Dutchwoman Kiki Bertens.

Former world No. 1 Azarenka, in only her second event after an eight-month absence because of a custody dispute involving her son, also looked sharp throughout her 6-2 6-2 win over 30th-seeded Pole Radwanska.

Up next for the 28-year-old is Czech fifth seed Karolina Pliskova. Sloane Stephens beat Spanish third seed Garbine Muguruza 6-3 6-4. German 10th seed Angelique Kerber beat Chinese qualifier Wang Yafan 6-7(1) 7-6(5) 6-3. 

Ukrainian fourth seed Elina Svitolina also advanced with a 7-5 6-4 win over Australian Ashleigh Barty.

French Open champion Jelena Ostapenko capped the night session with a 7-6(4) 6-3 triumph over ninth-seeded Czech Petra Kvitova.