Stuttgart, Germany (SportsNetwork.com) - French Open runner-up Simona Halep was a second-round winner, while former Wimbledon finalist Agnieszka Radwanska came up an opening-round loser at the Porsche Tennis Grand Prix.
The second-seeded Halep is the first player to reach the quarterfinals this week after outlasting game rising Spaniard Garbine Muguruza 3-6, 6-1, 6-3 in 1 hour, 48 minutes in Wednesday's nightcap, while former French Open finalist Sara Errani dismissed the seventh-seeded Radwanska 7-6 (10-8), 6-4 on the indoor clay at Porsche Arena.
The hot Halep has won 15 of her last 16 matches, including recent titles in Dubai and Indian Wells.
Meanwhile, rising Swiss teenager Belinda Bencic took out wild card and 2011 Porsche champion Julia Goerges of Germany 3-6, 6-3, 7-5.
Two other first-round matches saw Kazakhstan's Zarina Diyas double-bagel former Wimbledon runner-up Sabine Lisicki of Germany 6-0, 6-0 in 64 minutes and German Angelique Kerber get past American Alexa Glatch 6-2, 7-5.
In some second-round action on Thursday, top-seeded former world No. 1 Maria Sharapova will take on Kerber, third-seeded Wimbledon champ Petra Kvitova will face American Madison Brengle and fourth-seeded former No. 1 and 2011 Porsche runner-up Caroline Wozniacki will be opposed by Czech Lucie Safarova.
The French Open titlist and Australian Open runner-up Sharapova is the reigning three-time Stuttgart champ, having beaten Ana Ivanovic in last year's marquee finale.
The 2015 Stuttgart winner will earn $108,000 and a new Porsche 911 Carrera sports car.