Third seed Yulia Putintseva was forced to retire in her Japan Women's Open first-round match due to a lower back injury.
The French Open quarter-finalist was trailing to Anna Karolina Schmiedlova in Hiroshima on Monday, having lost the first set 6-2, when she called time on the clash after struggling throughout.
Although Schmiedlova profited to take the scalp of the Kazakh star, she would have preferred to defeat a fully-fit opponent.
"She had some problem with her back, probably, so it wasn't as I wanted it to be," Schmiedlova said. "But I'm very happy that I can play the second round here. I'm happy to be here and I really like this tournament."
Later in the day, Ajla Tomljanovic raced to a straight-sets win over over Fiona Ferro, as seventh seed Zheng Saisai defeated Alison Riske 7-5 6-4.
Luksika Kumkhum and Viktorija Golubic each came from behind to win on Monday, while Zhu Lin also booked her place in the second round, beating home hopeful Miyu Kato.