The US Open appears set to go ahead amid the coronavirus pandemic, and Nick Kyrgios is the latest top player to express reservations.
Some players have expressed concerns about playing at this year's US Open, but Patrick Mouratoglou thinks Serena Williams wants to be there.
Filip Krajinovic progressed at the expense of Novak Djokovic, but was unable to topple Dominic Thiem in the final.
Amid uncertainty over the US Open, Feliciano Lopez said Andy Murray was looking forward to the event.
Stefanos Tsitsipas beat Benoit Paire and Richard Gasquet defeated David Goffin at the Ultimate Tennis Showdown.
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.
Babe Ruth made a poignant final visit to Yankee Stadium 72 years ago, while Real Madrid ruled Europe for the first time in 1956.
Another two top-10 players cannot see how the US Open can take place unless there is a significant change of circumstances.
Former world number one Jelena Jankovic was like "a child in a candy shop" when she played doubles with Novak Djokovic.