Simona Halep claimed her fourth successive win over Venus Williams to reach the Miami Open quarter-finals.
The Romanian third seed hit 21 winners as she beat Williams 6-3 6-3 and faces the winner of an all-Chinese match between Wang Qiang and Wang Yafan next.
Either Halep or Petra Kvitova could replace Naomi Osaka as world number one at the end of the tournament.
Czech Kvitova beat France's Caroline Garcia 6-3 6-3 to reach her fifth WTA quarter-final of the year.
The second seed will play Ashleigh Barty next after the Australian fought back to beat Kiki Bertens 4-6 6-3 6-2.