Sharapova to face Radwanska
Defending champion Maria Sharapova defeated Anastasia Pavlyuchenkova 6-4 6-3 to set up a Porsche Grand Prix quarter-final clash with top-seeded Agnieszka Radwanska.
The sixth-seeded Sharapova needed little over an hour-and-a-half to defeat her fellow Russian, keeping alive her bid to win the tournament in Stuttgart for the third year-in-a-row.
"I'm pleased to have won in two sets, but I am never really happy with my performance and always want to improve," said Sharapova.
On her next opponent, the 27-year-old added: ""Radwanska is the number three in the world and everyone knows she plays extremely well, but I love challenges like this.
"There are no secrets to our games, we know each other very well, but have not played each other for a while on clay. It will be interesting and I'll have to improve in all areas."
Sharapova has now won 10 matches on the spin in Stuttgart, having lifted the trophy in the German city in both 2012 and 2013.
Polish world no 3 Radwanska, meanwhile, was rarely troubled in wrapping up her 6-3 6-2 win over Italy's Roberta Vinci in one hour and 19 minutes.
Fifth-seeded Jelena Jankovic battled back from a set down to see off Italian Flavia Pennetta 3-6 6-2 6-3 and set up a showdown with Alisa Kleybanova, who upset the third-seeded Petra Kvitova, for a place in the last four.
Ana Ivanovic also had to rally from a deficit to defeat German wild card Julia Goerges, the ninth seed from Serbia eventually winning 1-6 6-2 6-3
There was also disappointment for another home favourite, fourth seed Angelique Kerber going down in straight sets to Carla Suarez Navarro of Spain.