The 35-year-old, who secured all 10 of his career wins across his five seasons with the Mercedes, has now made a shock return to the team, backing up the duo of George Russell and young prodigy Kimi Antonelli.
Off-track, Mercedes will hope Bottas' experience can add a lot as they look to develop their car and get back to winning ways.
Valtteri Bottas will be a Mercedes reserve driver for 2025George Russell replaced Bottas at Mercedes in 2022
Bottas: Clear plan needed for F1 return
Although he will not be on the grid for lights out in Melbourne, Bottas has not given up on a return to the sport full-time, so long as the right opportunity presents itself.
He has admitted, however, that retirement is an option if that opportunity does not arise.