By Brian Homewood

STUTTGART, Germany (Reuters) - Caroline Wozniacki's ankle injury came back to haunt her Thursday as the top seed was knocked out of the Stuttgart Open in straight sets by Lucie Safarova.

Seven-times grand slam winner Justine Henin, who returned to the circuit in January after a sabbatical of just under two years, beat her Belgian compatriot Yanina Wickmayer, despite a nervous stutter in the second set .

World number two Wozniacki, who retired hurt during a match at the Family Circle Cup in Charleston two weeks ago after injuring her ankle in a tumble, said she was still struggling as she lost 6-4 6-4 in her first match in Stuttgart.

"I didn't feel I could move 100 per cent," the Dane told reporters after her defeat to the 38th-ranked Safarova. "She was making me run and that's why she won.

"If you can't move it's difficult to win."

Safarova said she sensed Wozniacki was vulnerable.

"She was not moving as well as she can," the Czech said. "I was trying to make her run and push her."

Henin, a wild card, took the first set 6-3 and then raced to a 5-1 lead before her nerves took control.

Wickmayer won four games in a row to pull level but Henin regained her composure to take the second set 7-5.

"I was controlling the match then suddenly I got nervous," said Henin.

"I was very pleased with my reaction at 5-5, I had to stay very calm."

Henin will face Jelena Jankovic Friday after the Serb, seeded four, beat Tsvetana Pironkova 6-2 6-2.

"I'm glad I can play this type of game, it's very important for me as I try to get my confidence back on clay," said Henin.

(Editing by Kevin Fylan and Alison Wildey; To query or comment on this story email sportsfeedback@thomsonreuters.com)