Mercedes team principal Toto Wolff says Valtteri Bottas will have to "justify" his place on the roster, with added scrutiny set to fall on the Finn in 2019. Bottas went winless across the 2018 campaign, despite Mercedes securing a fifth consecutive constructors' championship.
While Lewis Hamilton won 11 grands prix and a fifth drivers' crown, Bottas struggled to make an impact on the championship.
Esteban Ocon's return to Mercedes as a reserve driver in 2019 is set to put the pressure on even further and Wolff says Bottas must deliver to keep his seat.
"Every racing driver in a Formula 1 car has to look over his shoulder. It is a very brutal sport where only the best ones survive and they are very well aware," Wolff told Reuters.
"They have made the selection of the top 20 racing drivers in the world and every single year they have to justify that they deserve the place. It is not only valid for Valtteri but all the others as well."
Bottas saw chances to win in Shanghai and Baku slip through his fingers in the early rounds of 2018 before a likely win was taken away by Mercedes ordering him to let Hamilton through.
Wolff says those performances prove that Bottas can fight back next year.
"Valtteri is a fierce warrior and he wouldn't be where he is today if he was not an outstanding racing driver," said the Austrian.
"I think he absolutely embraces the challenge of being team mate and competitor to Lewis Hamilton.
"I think where things have gone wrong with Valtteri in 2018 was that he was very unlucky. He could have, should have — but that doesn't count — won three races."
GPFans is a multi-platform, multi-language brand dedicated to Formula One coverage. We bring you all the ins and outs of the sport, 24/7, everything from up-to-the-minute news and features to the latest viral stories and clips.
We believe that a new generation of exciting, outspoken drivers will make F1 more popular than ever before, and we want to give our users access to as much of their heroes as possible, on and off the track. From Lewis Hamilton to Max Verstappen, Daniel Ricciardo to Sebastian Vettel, we provide in-depth analysis of every every Grand Prix in the season, from Australia to Abu Dhabi.
With Formula One under the new ownership of Liberty Media, how the sport is being covered is evolving, and GPFans will look to be at the heart of this progression into new media, as one of the fastest-growing sites covering the king of motorsports.