Serena and Sharapova reach Miami quarters

Key Biscayne, FL ( - Six-time champion Serena Williams and Maria Sharapova were both fourth-round winners Monday at the Sony Open.

Williams, the world No. 1 and reigning U.S. and French Open champion, rolled to a 6-3, 6-1 win over Coco Vandeweghe, improving to 12-2 overall in 2014.

Williams, 32, improved to 3-0 lifetime against Vandeweghe and will meet German Angelique Kerber in the quarterfinals. Kerber, seeded fifth, outlasted No. 23 seed Ekaterina Makarova of Russia 6-4, 1-6, 6-3.

Williams' sister Venus, seeded 29th, lost to No. 10 seed Dominika Cibulkova of Slovakia, who gritted out a 6-1, 5-7, 6-3 victory.

Sharapova, the fourth seed, rallied past No. 19 seed Kirsten Flipkens 3-6, 6-4, 6-1 at Crandon Park.

Flipkens came out on fire and took the first set from Sharapova for the first time in her career.

The Belgian fell behind 4-0 in the second set before winning four of the next five games. But Sharapova held strong to take the second set, and then rolled to victory in the third.

Sharapova, a five-time runner-up in Miami, improved to 5-0 lifetime against Flipkens. The Russian advanced to play eighth-seeded Petra Kvitova, who came back to beat 12th-seeded Ana Ivanovic 3-6, 6-0, 6-0.

World No. 2 Li Na of China moved on with a 6-0, 6-2 win over Spain's Carla Suaraz Navarro and will play Denmark's Caroline Wozniacki, who eased past Varvara Lepchenko 6-0, 6-1.

Third-seeded Agnieszka Radwanska of Poland beat Ukraine's Elina Svitolina 7-6 (7-5), 5-7, 6-2 and will face Cibulkova in the quarters.

The 2014 Miami champ will collect $787,000.