Stephens downs Muguruza as seeds tumble in Miami

Sloane Stephens powered past world number three Garbine Muguruza as the seeds continued to fall at the Miami Open on Monday.

Sloane Stephens returns to Garbine Muguruza on Monday.

Sloane Stephens powered past world number three Garbine Muguruza as the seeds continued to fall at the Miami Open on Monday.

US Open champion Stephens dominated Spain's reigning Wimbledon champion Muguruza to record a 6-3, 6-4 win and advance to the quarter-finals.

Stephens, the world number 12, will face either Germany's Angelique Kerber or China's Wang Yafan for a place in the semi-finals.

Muguruza had been the highest ranked player left in the women's draw following the early exits of world number one Simona Halep and Caroline Wozniacki in the earlier rounds.

Earlier Monday, Czech fifth seed Karolina Pliskova booked her place in the last eight after opponent Zarina Diyas retired in the second set.

Pliskova was leading 6-2, 2-1 when the Kazakh player abandoned with an injury.