This was reported by the press service of the tournament.
Currently, Rublev is sick with coronavirus.
The reasons for the withdrawal of Karatsev and Donskoy from the tournament are still unknown.
The Russian national team for the ATP Cup included Daniil Medvedev, Roman Safiullin and Evgeny Karlovsky.
The team captain will be French Gilles Servard, who is Medvedev's coach.
The ATP Cup will be held from 1 to 9 January 2022 in Sydney, Australia.
The Russian national team is the current winner of the competition.
Earlier it was reported that Rublev fell ill with coronavirus before the start of the ATP Cup.