Top-seeded Victoria Azarenka pulled out of the Mexico Open in Acapulco on Wednesday with a left wrist injury, sending Dominika Cibulkova into the third round.
Azarenka was playing her first event since falling in the quarter-finals of the Australian Open to eventual champion Angelique Kerber.
The former world number one from Belarus, now ranked 14th in the world, had needed two hours to beat Slovenia’s Polona Hercog in three sets in the first-round on Tuesday.
Wednesday’s withdrawal from the ATP and WTA hardcourt tournament was another setback for a player who displayed strong form early in 2016, having apparently moved on from the injuries and personal issues that hampered her career over the past two years.
Slovakia’s Cibulkova next faces either Sweden’s Johanna Larsson, the sixth seed, or American Shelby Rogers.