LONDON (Reuters) - Sebastian Vettel has a big season ahead of him at Ferrari and could feel the heat from new team mate Charles Leclerc, retired Formula One world champions Jenson Button and Nico Rosberg said on Monday.
The 31-year-old Vettel, a four times world champion, lost out to Mercedes' Lewis Hamilton last year after the German and his team made some costly mistakes after a strong start to the campaign.
Ferrari have brought in Leclerc, 21, as a replacement for 2007 champion Kimi Raikkonen and replaced team principal Maurizio Arrivabene with long-time insider and technical head Mattia Binotto.
"The pressure is on, absolutely," Vettel's compatriot Rosberg told Sky Sports television.
"He (Vettel) was feeling it, I'm sure, already last year, and especially driving for Ferrari -- that's where the pressure is the highest because you've got the whole country on you," added the 2016 champion.
"He needs to improve and the team needs to improve overall. They just had too many mistakes last year because possibly they should have won it."
Button, who is joining Rosberg as a Sky pundit for the season that starts in Australia on March 17, said the arrival of Monageqsque Leclerc could have a similar effect to that of Daniel Ricciardo's debut season at Red Bull.
Ricciardo teamed up with Vettel at Red Bull in 2014, ending the season third and with three race wins while the German won nothing and finished fifth overall, moving to Ferrari at the end of the year.
"It's going to be a big year for Sebastian, I think. When Daniel Ricciardo came into Red Bull he found it difficult," said Button.
"Daniel put him under a lot of pressure and actually outperformed him. I think if Charles can do that this year it's a tough decision of where Sebastian is going to go for the future and what he's going to do.
"Charles seems such a happy-go-lucky guy, very relaxed, and I think the team are really going to take to him. And that sometimes can hurt the other driver," added the Briton, who won his title with Brawn GP in 2009.
Button also expected his fellow Briton and former McLaren team mate Hamilton, now a five times champion, to relish the challenge of regulation changes and new rivals.
"It's when the challenges stop that you decide 'you know what, I'm going to do something else'," he said. "But with the way Formula One is, with the regulation changes and the driver changes, he will want to keep going."
(Reporting by Alan Baldwin, editing by Ken Ferris)