Novak Djokovic has pledged financial support to Ukrainian tennis player Sergiy Stakhovsky, who has joined the fight to protect his country from the Russian invasion.
Stakhovsky, who famously beat Roger Federer at Wimbledon in 2013, last week said he had signed up for Ukraine's military reserves.
The former world number 31 on Sunday posted a screenshot on Instagram of a WhatsApp conversation with Djokovic.
"Thinking of you... hope all calms down soon," read a message from the Serbian 20-time Grand Slam champion to Stakhovsky.
"Please let me know what would be the best address to send help. Financial help, any other help as well..." wrote Djokovic.
The 36-year-old Stakhovsky retired after the Australian Open in January and has returned to Kyiv to take part in the struggle to repel the Russians.
A number of Ukrainian sports stars have joined the effort to defend their country, including two-time Olympic boxing gold medallist Vasiliy Lomachenko and world heavyweight champion Oleksandr Usyk.