Bottas was winless in 2018 for Mercedes - who won yet another constructors' championship. Lewis Hamilton claimed his fifth world title as the Silver Arrows proved too good yet again.
The Finn secured nine podium finishes for former side Williams - completely outperforming former F1 title contender Felipe Massa in Grove.
His form earned him a call-up to Mercedes - who were left with just one driver after Nico Rosberg's shock retirement three years ago.
Esteban Ocon is the Mercedes reserve driver this season and he has been tipped to replace Bottas in 2020, if the driver has another underwhelming season.
Asked whether he felt he needed to prove anything in the upcoming season by Motorsport.com, Bottas replied: "Well, first of all I feel I still haven't achieved anything in Formula 1 - so for myself I still have a lot to achieve.
"I do want to meet my targets. So, yes, I still have a lot to do in Formula 1.
"I feel like I have nothing to prove for anybody else, except me. The team knows exactly what I am capable of doing, but it's going to be up to me, and us as a team, to work hard to be able to perform on my best level all of the time.
"And I know exactly what I can do if I can perform at my very best."