Top seed Amelie Mauresmo withdrew from the Stuttgart Grand Prix without playing a match on Thursday, suffering from a right shoulder strain.
The French world number one added her name to a tournament injury list that includes Kim Clijsters, Justine Henin-Hardenne and Anastasia Myskina, all of whom pulled out before the tournament began.
"On Monday during practice I felt something on the serve, and obviously I was hoping it was nothing too serious, which was not the case," Mauresmo told reporters.
Mauresmo's place in the draw was taken by American lucky loser Lisa Raymond, who was beaten 6-4, 6-2 by Michaella Krajicek of the Netherlands. Krajicek next faces Tatiana Golovin of France, who beat Czech Iveta Benesova 6-4, 6-3.
The $650,000 event lost another leading player when sixth seed Russian Dinara Safina was upset 6-2, 6-2 by Slovak Daniela Hantuchova.
It was Hantuchova's first victory over a top 10 opponent since she defeated Patty Schnyder in Sydney in the second week of the year and follows two previous defeats by Safina, the most recent last week in Luxembourg.
"Even the match last week, I came off the court feeling very well because it was a very good match," said Hantuchova. "There was not much I did wrong, so coming into today's match I felt if I just did a few things better here and there I could take this one."
Fifth seed Schnyder was also stretched before the Swiss left-hander emerged from a two hour 14-minute battle with Israel's Shahar Peer with a 7-6, 2-6, 6-4 victory, clinched on her fifth match point.
Some fine serving played a large part in fourth seeded Russian Nadia Petrova's 6-3, 6-4 win over Anna-Lena Groenefeld of Germany.
Petrova, still trying to regain the form that earned her four titles this year before injury stalled her progress, was troubled in a 12-minute opening game in which she fought off four break points, and when she survived three break points when leading 2-1 in the second set.
In the remaining second round match, eighth seed Jelena Jankovic of Serbia hobbled her way to a 4-6, 6-2, 7-5 win over Bulgaria's Tsvetana Pironkova.
Fighting off leg cramps in the final set, Jankovic served for the match at 5-2, 5-4 and 6-5 before finally securing a two hour 35-minute victory.
