Cape Town - Mercedes motorsport director Toto Wolff says it is time for Valtteri Bottas to "step up" and prove that he is ready for "race wins and for championships."
The Finn has joined Mercedes ahead of the 2017 championship, called up to fill the seat vacated by 2016 World Champion Nico Rosberg.
It is a huge challenge for the former Williams driver, but one that Wolff believes he can rise to.
"Valtteri is a no-nonsense guy: down to earth, straightforward and very focused," said the Austrian. "Pretty Finnish, to be honest, and a great fit for us.
"He has an impressive track record in the junior categories and nine podiums in F1.
"But now it's time for the next level, to see how he can step up to challenge for race wins and for championships.
"We have confidence in Valtteri's ability and it's one of the reasons that he is the driver we set our sights on this winter.
"One thing is for sure: as I know Valtteri, he will give it everything."
Bottas has a month to adjust to life at Mercedes before the team launches their new car on February 23, just days prior to pre-season testing in Spain.
Wolff added: "Sometimes in life, unexpected circumstances provide interesting opportunities.
"Nico's decision in December was a big surprise - certainly a challenging situation for the team to handle. But weathering the storm makes you more resilient and we see this as another opportunity for the team to grow."
"The next weeks will be busy as we work to build relationships so Valtteri understands the team and the car. But that's an exciting challenge that will bring us fresh energy and a new dynamic between the drivers.
"And, of course, we're working hard to give Lewis and Valtteri the car they need to do the job."