Kerber, Pliskova reach Miami quarters, Muguruza retires

Mar 27, 2017; Miami, FL, USA; Caroline Wozniacki of Denmark hits a forehand against Garbine Muguruza of Spain (not pictured) on day seven of the 2017 Miami Open at Crandon Park Tennis Center. Mandatory Credit: Geoff Burke-USA TODAY Sports

(Reuters) - Top seeds Angelique Kerber and Karolina Pliskova reached the Miami Open quarter-finals while French Open champion Garbine Muguruza retired from her match with Caroline Wozniacki after dropping the first set.

German Kerber, the top seed, cruised by Japanese qualifier Risa Ozaki 6-2 6-2 while Czech second seed Pliskova beat 15th-seeded compatriot Barbora Strycova 6-1 6-4.