Fourth seed Kurumi Nara fell at the first hurdle as she was knocked out of the Baku Cup following a straight-sets defeat to Olga Savchuk on Tuesday.
The 23-year-old Japanese followed out fellow seeds Dominika Cibulkova, Bojana Jovanovski and Francesca Schiavone - who were defeated the previous day - with a 6-3 6-2 loss in 86 minutes to the Ukrainian qualifier.
Seventh seeded Russian Vitalia Diatchenko battled for a 6-3 6-4 victory over qualifier Nigina Abduraimova of Uzbekistan on the opening match on Centre Court to set up a second-round clash with Kirsten Flipkens.
Belgium's 2013 Wimbledon semi-finalist Flipkens was pushed to three sets but she held on to see off Turkey's Cagla Buyukakcay 6-1 6-7 (3-7) 6-4 in the final match of the day.
Lin Zhu of China claimed a 3-6 7-5 6-3 comeback victory over Kristyna Pliskova of the Czech Republic in a match lasting two hours and five minutes on Court Three.
In the opening match on Court One, Ukraine's Kateryna Bondarenko eased past qualifier Valentyna Ivakhneko 6-1 6-2 to set up a clash with another Russian in top seed Anastasia Pavlyuchenkova.
China's Zhaoxuan Yang advanced after going 6-3 up in the first set against Yulia Beygelzimer of Ukraine, who was forced to retire, and there were also wins for Romania's Patricia Maria Tig and Estonia's Anett Kontaveit at the expense of Olga Ianchuk of Ukraine and Japan's Misa Eguchi.