Emma Raducanu pulled out of her ASB Classic second round match in tears after injuring her ankle just 11 days before the start of the Australian Open.
The 20-year-old Briton won the first set 6-0 against Slovak Viktoria Kuzmova, but lost the second 7-5.
She received medical treatment before the start of the third set but signaled her two-point withdrawal in her first service game.
The former US Open champion had an injury-blighted 2022 season.
After retiring from five matches last year, Raducanu said she was injury-free and feeling “good” after an exhibition game in December.
She started 2023 with victory over teenager Linda Fruhvirtova in their opening game in Auckland in preparation for the first major tournament of the season in Melbourne.
Elsewhere on Thursday, Coco Gauff beat fellow American and 2020 Australian Open winner Sofia Kenin 6-4 6-4.
The 18-year-old number one seed will play in the quarter-finals against China’s Zhu Lin, who beat seven-time Grand Slam singles champion Venus Williams 3-6 6-2 7-5 in a rain-interrupted match.
Zhu won the last four games of the match as she trailed 5-3 in the deciding set. Williams served for the match at 5-4 but the Chinese world number 84 broke and saved four break points as she held serve to advance 6-5 before breaking serve again.
