BERLIN (Reuters) - Germany's Angelique Kerber beat sixth seed Ekaterina Makarova 6-3 6-2 in the Stuttgart Grand Prix quarter-finals on Friday to record her second upset win in two days.
The world number 14, who ousted title holder Maria Sharapova on Thursday, will next meet unseeded American Madison Brengle.
Russian Makarova started well and went 3-0 up but Kerber roared back, taking the ball early and attacking at every opportunity to win the next seven games while her opponent littered the indoor arena with unforced errors.
"I am kind of speechless. It's just amazing to be on center court," said the unseeded Kerber who had a bad start to the year but won a tournament in Charleston, South Carolina earlier this month.
"I have rediscovered my joy and passion for tennis and I am enjoying every minute," she told reporters.
Brengle, 25, had to battle back from a set down to beat Caroline Garcia of France 3-6 6-3 6-3.
World number three Simona Halep eased past Sara Errani of Italy 6-4 6-4 as the Romanian set up a meeting with former number one Caroline Wozniacki.
Dane Wozniacki had an even easier task, crushing eighth seed Carla Suarez Navarro of Spain 6-0 6-3.
Reporting by Karolos Grohmann, editing by Tony Jimenez