Maria Sharapova fought her way into the semi-finals of the LA Championships on Friday with a 6-4, 7-5 win over Polish teenager Urszula Radwanska.
Sharapova will face Flavia Pennetta in the last four after the Italian stunned second seed Vera Zvonareva of Russia 6-4, 6-2. Romania's Sorana Cirstea upset Agnieszka Radwanska, Urszula's older sister, to set up a semi-final against Samantha Stosur, who beat Zheng Jie of China.
Three-times Grand Slam champion Sharapova endured some erratic groundstrokes and patchy service games but used her vast experience to down the temperamental Pole.
The Russian was clearly frustrated with her lack of service consistency.
"I made a lot more errors than I wanted to," said Sharapova, who double faulted 13 times.
"I created so many bad habits. Eventually it's going to work itself into place. But her second serve, she was hitting 70 mph and I was pounding on it."
Cirstea upset the elder Radwanska 7-6, 1-6, 7-5 and will now face Australian Stosur, who reached her second consecutive semi-final with a 4-6, 6-3, 6-4 win over China's Zheng.
Cirstea received treatment for a right foot injury during the second set but hopes to be ready for Stosur.
"I think I'm learning a lot," said the 19-year-old.
"I am still young. If I keep going like this, I think I can improve a lot."
Last week, Stosur upset Wimbledon champion Serena Williams at the Stanford Classic before falling to eventual winner Marion Bartoli.
"I'm very happy with the way things have gone, to make two semis in two weeks," she said. "It's definitely been a goal of mine to try to win a singles title. I'm going to give it my all to win one."