Wimbledon champion Elena Rybakina pulled out of the Eastbourne International on Monday due to a viral illness, raising doubts over her defence of the title at the All England Club next week.
The world No 3 had been scheduled to play Wang Xiyu on the first day of main draw action at Eastbourne.
Rybakina also withdrew ahead of her third round match at the French Open citing illness earlier this month and fell to a shock defeat to Donna Vekic in the second round of the German Open last week.
The Kazak's absence meant that Russian Daria Kasatkina was the highest ranked player in action on Monday as she beat Ukrainian Anhelina Kalinina 6-3, 6-1 in a politically-charged match.
Kasatkina will face Karolina Pliskova in round two after the Czech advanced when Elise Mertens retired in the deciding set of their clash.
Dubai-based world number 11 Kasatkina, who was banned from competing in Britain last year due to the ongoing conflict in Ukraine, acknowledged that Ukrainians are in a "way worse situation" and conceded she cannot see an imminent end to the fighting.
"My family, my parents are still in Russia," she said. "As you can see, the last few days it's been a big mess also there.
"It's been a tough year, and we don't know how long it's going to be. Honestly, so far I don't see the end.
"(It) feels shit, honestly. I'm not going to hide it. It's tough to face the circumstances for such a long time already," said Kasatkina, who was booed off court earlier this month following her defeat by Ukraine's Elina Svitolina at the French Open.
"I'm just trying to be a good human in this scenario. That's all I can do."
There was some joy for the home fans as Brits Harriet Dart and Jodie Burrage came through tough three-set encounters against China's Zhang Shuai and American Lauren Davis respectively.
Jessica Pegula, Ons Jabeur, Coco Gauff and Petra Kvitova are among the big names in action on Tuesday.