Simona Halep had a double boost on Wednesday as she booked a Madrid Open quarter-final spot and secured her place at the top of the world rankings for another week.

Halep cruised past Kristyna Pliskova 6-1 6-4 to secure her place in the last eight – the Romanian yet to drop a set this week – before watching rival Caroline Wozniacki exit.

Wozniacki was the only player who could have usurped Halep this week but she needed to win the tournament, her hopes of that feat ended by defeat to Kiki Bertens in round three.

There were no such problems for Karolina Pliskova as she eased past Sloane Stephens 6-2 6-3, setting up a meeting with Halep on Thursday.

Caroline Garcia, Carla Suarez Navarro and Petra Kvitova also picked up wins, while Maria Sharapova is into the last eight of a Premier-level event for the first time in 12 months after overcoming Kristina Mladenovic.

ONE PLISKOVA DOWN, ONE TO GO

Two-time defending champion Halep looks a class apart in the opening days of the tournament, and has only been broken once in three matches.

Kristyna Pliskova was no match for the Romanian, but Halep knows she faces a tougher test against Karolina in the quarters.

"I feel like it was a very good match, the hardest [I've had] here," she said of the win over Kristyna. "She improved a lot since last year, we played together here, and she was different player.

"It's always tough to play against the sisters. I know the match will be very tough and I will be ready. I will focus on myself, like every match, and we'll see what is going to happen."

BERTENS' BEST WIN

All eyes were on Wozniacki ahead of her clash with Bertens, but the world number two was out of sorts and got punished.

For Bertens, though, the 6-2 6-2 triumph was a memorable moment in the 26-year-old's career.

"I think one of my best matches ever," she said. "I'm really happy to be back here in Madrid - I think so far all the matches I've played here have been going very well.

"I was just going out there very calm, just going for my shots, and trying to play aggressive where I could. And of course if you hit almost everything in everything feels perfect!"

ALL OVER FOR MUGURUZA

Garbine Muguruza's hopes of becoming the first home winner are over after she was beaten by Daria Kasatkina.

Having levelled the match Muguruza found herself in real trouble at 4-1 down in the decider, and could not mount a comeback despite Kasatkina spurning eight break chances in the sixth game, as the Russian sealed a 6-2 4-6 6-3 triumph and a meeting with Kvitova.