Agnieszka Radwanska of Poland hits a return to Victoria Azarenka of Belarus during their women's singles quarter-final tennis match at the Australian Open 2014 tennis tournament in Melbourne January 22, 2014.  [Photo/Agencies]

"In the second set I managed to fight back. Third set, the first game was important. I let it go, like easily let it go. From there just couldn't get back to it. It was tough."

Radwanska was also safe on her own serve, dropping just two games in the two-hour match while breaking Azarenka six times. She hadn't beaten Azarenka in their last seven matches, and had only won three of their previous 13.

"I said to myself one day I have to have one step forward and do the semifinal, and I'm so, so happy that I did it finally," Radwanska said of her first run to the semis of a major on hard courts. She reached the final at Wimbledon in 2012, becoming the first player from Poland to reach a major final in the Open Era, and the semifinals last year.

"I just had to play my best tennis, even better and play aggressive and go for every shot I could,'' Radwanska said of her win over the two-time defending champion.

Azarenka went down in a flurry of unforced errors, making 47 in three sets as she tried to push Radwanska around.

She seemed to have momentum at the end of the second set, when she leveled after breaking in the last game. But she didn't carry it through, pushing a forehand fractionally too wide on the first point and unsuccessfully challenging the out call.

It was a sign of things to come. She won only 14 points in the third set, and was broken three times.

Azarenka was booed late in the match, when she smashed a ball into the back of the court after another frustrating error. She screamed loudly after losing big points to the incredibly consistent Radwanska, punched her thigh and her racket and even slapped the court. Nothing worked to change her fortunes.

"I'm not happy with what I did today, but on the court I felt like I could have played a lot better," Azarenka said. "I can't take away what she's done today. She played amazing."