Azarenka, Sharapova lead charge in Stuttgart

World number one Victoria Azarenka, second-ranked Maria Sharapova and number three Petra Kvitova begin their French Open build-up on Monday at the star-studded $740,000 Stuttgart tournament.

Belarusian Azarenka, the Australian Open champion, returns to action for the first time since losing her 26-match winning streak to Marion Bartoli in the quarter-finals of the Miami hardcourt event.

That loss came after a breath-taking start to 2012 in which the 22-year-old had captured four titles, including her first Grand Slam crown.

Sharapova, who turned 25 on Thursday, was beaten by Azarenka in the Melbourne final and in the Indian Wells title match before losing in the Miami final.

The Russian star, who has yet to make the final of the French Open, falling in the semi-finals twice, believes she has developed a better understanding of claycourt tennis as her career has progressed.

"I feel like I've improved with every year that I have been playing on it and I enjoy it," she said.

"I feel like you learn so much about the construction of the points and the games -- such a cat-and-mouse game. I didn't necessarily like that many years back, but I feel like I'm much better at it and I have improved physically as well."

After local favourite Julia Goerges won the 2011 Stuttgart title, world number 11 Andrea Petkovic is the top-ranked German for this week's tournament.

China's Li Na, eighth in the world, Australia's Samantha Stosur, fifth, and former world number one Caroline Wozniacki of Denmark are all part of the powerful line-up.

With Germany desperate for a new star since Steffi Graf dominated women's tennis in the 1990s, Petkovic is leading Germany's tennis revolution.

She reached the last eight at the Australian Open in 2011, the first German to reach a Grand Slam quarter-final since 2006.

The 24-year-old followed that up by reaching the quarters of the French and US Opens, the only player all year to make the final eight at three of the four Slams.

Having started 2011 ranked 32nd in the world, she reached a high of ninth in December and is back playing after a back injury robbed her of three month of tennis since injury struck in January.

Goerges followed Petkovic in the German revival by overpowering Wozniacki in the final here last year with huge serves and groundstrokes on her way to collecting her first Premier title.

"I had goosebumps at match point," Goerges said of the Stuttgart final. "It was an unbelievable feeling playing the final with so many people watching."