Azarenka digs deep to beat wildcard Barthel

Belarus' Victoria Azarenka serves against German Mona Barthel during their quarterfinal match at the Porsche tennis Grand Prix in Stuttgart, Germany, Friday, April 27, 2012. AP/Michael Probst)

STUTTGART, Germany – World number one Victoria Azarenka admitted she had been in a battle royal after her 6-4, 6-7 (3/7), 7-5 win over wildcard Mona Barthel put her in the semi-finals at Stuttgart’s WTA tournament.

Having already beaten ex-world number one Ana Ivanovic and seventh-seed Mario Batroli on the way to the quarter-finals, Barthel put up another battling performance to take Friday’s game to three sets despite losing the first.

This was Azarenka’s fourth win over the 21-year-old German this year, but the world’s top player needed nearly three hours to see off the German wildcard at the clay-court tournament.

“She keeps producing some great tennis and she showed again today why she is a tough one to beat,” said Azarenka after Barthel blasted down 13 aces compared to her five.

“Her serve is definitely up there with the best, after more than two-and-a-half hours she was still blasting down aces.

“I have been saying for a while she is one to watch.”

In the semi-finals, Azarenka faces Poland’s Agnieszka Radwanska who earlier beat French Open champion Li Na of China in her quarter-final.

Li went down 3-6, 6-2, 6-3 to the Polish fourth-seed, despite dominating the first set.

The Chinese struggled to cope as Radwanska raised her game with a series of drop shots and strong returns in the second before carrying her improved form into the third.

“I was more aggressive in the first set, but things turned after I broke her serve in the second,” said 30-year-old eighth-seed Li.

“I didn’t get many first serves in after that and it left me pretty down, I was really pissed off at myself walking off court.

“At least, I know I can still slide out there, I haven’t played badly in my three games this week, so at least I know I can continue on the right path.”

With Roland Garros to start on May 27, Radwanska said she was enjoying finding her feet on clay courts as she bids to win her first Grand Slam title.