The path has now been formally cleared for Mercedes to confirm George Russell as Bottas' replacement, which is expected to be announced on Tuesday.
Revealing the difficulties behind the move, especially, as the Finn and Lewis Hamilton have helped Mercedes win four consecutive constructors' championships as a duo, Wolff said: “This hasn’t been an easy process or a straightforward decision for us.
“Valtteri has done a fantastic job over the past five seasons and he has made an essential contribution to our success and to our growth.
“Together with Lewis, he has built a benchmark partnership between two team-mates in the sport, and that has been a valuable weapon in our championship battles and pushed us to achieve unprecedented success.
“He would absolutely have deserved to stay with the team, and I am pleased that he has been able to choose an exciting challenge with Alfa next year to continue his career at the top level of the sport.
“When the time comes, he will leave us with huge goodwill from every single member of the team, and he will forever be part of the Mercedes family.”
Bottas has so far competed in 92 grands prix with Mercedes, winning nine and claiming 17 pole positions.
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