Nico Rosberg has warned Sebastian Vettel that he cannot afford to perform at the same disappointing level as he did in the 2018 season, as he now has a team-mate in the form of Charles Leclerc who will take advantage of any slips to become Ferrari's top driver.
Leclerc was impressive in the lower levels of motorsport before making his debut in Formula 1 last year with Sauber, where he continued performing positively.
Ferrari took the option to promote him to the team in 2019 at the expense of Kimi Raikkonen, and Rosberg has challenged the Monegasque driver to challenge Vettel to become the Scuderia's number one.
"Leclerc at Ferrari is exciting because he's fast - very, very fast," Rosberg told Marca.
"He has all the tools to be a world champion, and against Sebastian, who has always had a clear number two but that time is over. He [Leclerc] has everything to be the number one and that's exciting to see.
"Sebastian doesn't have the luxury to have another season like last year or he'll be beaten by his teammate. He has to act now and that will be very, very fun."
Last year it was clear that Vettel was the number one ahead of Raikkonen, and Rosberg is excited to see a duel for the top position - which he hasn't seen since Felipe Massa and the Finn years ago.
"It's interesting to see how Ferrari will handle this because as far as I can remember, they've always had a number one and a number two," the German continued.
"For 11 years. The last time was Kimi [Raikkonen] against Felipe [Massa]. That will be brilliant, to see how they handle it internally, and how much they'll respect Leclerc.
"It will be a lot of fun."