Czechs Petra Kvetova qualified for the quarterfinals of the Miami Open after beating Frenchwoman Caroline Garcia 6-3 6-3 in the fourth round and Kvetova could lead the world ranking if she won the Miami title.
In the quarter-finals, Kvetova will meet Australia's Ashley Barty, who beat Dutchman Kiki Bertins 4-6, 6-3 and 6-2.
Annette Contavet, from Estonia, qualified for the quarterfinals after the departure of Canadian rival Bianca Vanessa Andrescu.
In the men's category, Australian Jordon Thompson qualified for the knockout round with a 7-5 victory and 7-5 over the Bulgarian Gregor Dimitrov.
Thomson will meet South African Kevin Anderson, who beat Portuguese João Sosa 6-4, 7-6 (8/6).