Boris Becker and Nick Kyrgios were involved in a tense Twitter stand-off over the Australian's criticism of Alexander Zverev.
Australian Nick Kyrgios blasted Alexander Zverev, who was apparently spotted partying.
Having lost one of his two opening-day matches last weekend, Novak Djokovic won both encounters in Zadar on Saturday to reach the final.
The Belgrade crowd will not get to see Novak Djokovic in the final of the Adria Tour exhibition event at the Novak Tennis Centre.
As the Adria Tour got underway, Novak Djokovic was beaten for the first time this year.
Dominic Thiem dan Alexander Zverev mengundang keraguan sama ada Terbuka Amerika Syarikat (AS) akan diteruskan seperti yang dijadualkan selepas diselubungi wabak COVID-19.
Another two top-10 players cannot see how the US Open can take place unless there is a significant change of circumstances.
World number one Novak Djokovic said he was able to use a tennis court almost every day during lockdown in Marbella.
German tennis star Alexander Zverev discussed coronavirus, which has wreaked havoc across the world.
Rafael Nadal powered through to the last eight but second seed Alexander Zverev fell on Wednesday, while Grigor Dimitrov survived.