PARIS — When Simona Halep and Andrea Petkovic played a year ago in the final of a tournament in Nuremberg, Germany, Halep was ranked 58th and Petkovic 103rd.

Today, they will play in the French Open semifinals, with Halep ranked fourth and Petkovic 27th. One of them will advance to her first Grand Slam final.

Petkovic, 26, overpowered Sara Errani, 6-2, 6-2, Wednesday to become the first German woman to reach the semifinals here since Steffi Graf in 1999.

Using guile and spectacular shot-making, Halep, 22, defeated Svetlana Kuznetsova by the same score. She is trying to become the first Romanian woman in the final at Roland Garros since her manager, Virginia Ruzici, in 1980.

Petkovic was in her fourth Grand Slam quarterfinal, but her first in three years.

After being troubled by injuries and considering retirement a year ago, Petkovic is closing in on her 2011 levels, when she was a top-10 player.

“I was the happiest when I was in the top 10 and was one of the top players, and then it was just taken away from me,” she said. “So now every time I have happy moments and nice wins, it immediately brings the doubt and the fear of that it might slip away again.”

She said her comeback, aided by her new coach, Eric van Harpen, was “still not at the end.”

Halep, who is also in her first career Grand Slam semifinal, is rising in a different way.

She has collected seven titles in the past 13 months, her first coming against Petkovic in Nuremberg. But she had not made a splash at a major until now.

“She plays always very smart tennis,” Kuznetsova said. “She doesn’t overpower you. She takes off the speed very well.”