French Open champion Li Na and former world number one Jelena Jankovic were both forced to withdraw from the WTA Paris Indoor Open on Tuesday.
Chinese number one Li, seeded third at the event, withdrew while trailing Bulgarian Tsvetana Pironkova 7-6 (7/5) 3-2 in their first round clash at the Paris-Coubertin Stadium.
The world number nine was visibly suffering with a back problem and finally called it a day after receiving treatment courtside.
World number 13 Jankovic, the fourth seed, also pulled out of the tournament after failing to recover from the left thigh injury she picked up in Serbia's recent Fed Cup World Group first round victory over Belgium.
"I had hoped that after treatment I could still play here but unfortunately it's impossible," said Jankovic.
The Serb was scheduled to play Yanina Wickmayer in round one.
Germany's Mona Barthel advanced to the second round after beating Barbora Zahlavova Strycova of the Czech Republic 6-3 6-2, while another Czech Petra Cetkovska advanced past Italy's Alberta Brianti 6-3 6-3.
There were no such problems for German sixth seed Julia Goerges, who needed just 51 minutes to beat Israel's Shahar Peer 6-1 6-3, or ninth seed Angelique Kerber, who beat Lucie Safarova 6-2 7-6 (7-3).
There were also wins for Chanelle Scheepers, Petra Cetkovska and Petra Martic.
