Miami: World number one Serena Williams breezed into the quarter-finals of the WTA and ATP Miami Masters on Monday while Russian fourth seed Maria Sharapova battled through three sets to advance.
Top-seeded defending champion Williams routed US qualifier Coco Vandeweghe 6-3, 6-1 in 78 minutes to book a last-eight matchup with German fifth seed Angelique Kerber.
Sharapova rallied to defeat Belgium's Kirsten Flipkens 3-6, 6-4, 6-1 after two hours and four minutes while Kerber took six minutes longer to eliminate Russia's Ekaterina Makarova 6-4, 1-6, 6-3.
Williams smashed 17 winners to only 11 unforced errors and denied her compatriot on all six of her break-point chances to book her 13th quarter-final in 14 Miami appearances.
"It was a much tougher match than the scoreline showed," Williams said. "Coco has such an amazing serve, so every time I was returning I was like, 'Hopefully I can touch the ball.' But it was really good for me to win this match."
Williams owns a 3-1 career edge over Kerber, whose lone win came two years ago on Cincinnati hardcourts.
"Angelique is really good and moves really, really well," Williams said. "I feel better than I did in my first few matches, though, so I hope I can keep going forward."
Four-time Grand Slam champion Sharapova, a five-time Miami runner-up, is still seeking her first title at the hardcourt event.
"Of course it would be meaningful for me to win this tournament after being so close. Definitely," Sharapova said.
"Of course you want to be able to hold the winner's trophy, but you also know the matches you've got to get through to get to the final stage.
"It's not like I didn't have my opportunities in those finals. I just didn't take them. That's why you come back and hope for another chance."
Sharapova made 10 double faults, half of them in the first set, and served no aces but improved as the match progressed and in the final set won five of 12 points off the Belgian's first serve and seven of nine off her second serves.
"I didn't start off the way I wanted to," Sharapova said. "Nothing was working. Just the way it went in the beginning."
Next up for Sharapova will be the winner of a later match between Serbian 12th seed Ana Ivanovic and Czech eighth seed Petra Kvitova.
Men's world number one Rafael Nadal was set to meet Uzbekistan's Denis Istomin in a later men's third-round match-up.
Canadian 12th seed Milos Raonic blasted 10 aces in defeating Spaniard Guillermo Garcia-Lopez 6-1, 6-2 in 56 minutes.
The Montenegrin-born big server, who droped only five points on his serve in the match, reached the last 16 at Miami for the first time after being forced to withdraw from third-round matches with injuries the past two years.
"I just generally improved, especially on second serve returns (and) taking advantage more of those opportunities," Raonic said.
He next faces German Benjamin Becker, who ousted Slovenia's Aljaz Bedene 6-3, 7-5.
"It's going to be a tough match (next) but it's up to me," Raonic said. "I've got to play well. If I do, I can always give myself an opportunity to do well."
Ukraine's Alexandr Dolgopolov waited through a third-set rain delay before dispatching Serbian Dusan Lajovic 3-6, 6-0, 7-6 (7/5). Dolgopolov could face reigning Australian Open champion Stanislas Wawrinka in the fourth round.