As the teams get ready for the season opener in Australia, presenter, pundit and former driver David Coulthard has said that the arrival of Charles Leclerc at Ferrari will provide a threat to Hamilton's chances of a sixth world championship.
Coulthard says that Ferrari's new line up will provide a more dynamic challenge to Hamilton. He believes that Leclerc will motivate Vettel and push him harder than Raikkonen did last year.
"As far as Lewis is concerned, the pairing of Sebastian and Charles has a much more dangerous look to it, in my opinion, than that of Sebastian and Kimi."
Coulthard says that he did not expect Raikkonen to have won many races last season but he fully expects to see Leclerc on the podium spraying champagne this year.
"He is young enough, enthusiastic enough and fast enough to be pushing Sebastian onwards, and that will keep not just Seb on his toes, but Lewis as well."
Ross Brawn added his opinion on the Vettel vs Leclerc debate saying that he thinks that Leclerc is unlikely to beat Vettel during his first season at Ferrari: "I'd be surprised, if I'm honest, Sebastian is very good."
Brawn does believe that Leclerc could unsettle Vettel and that might take some careful management from the team. He also said that Leclerc is going to be the one to watch for 2019.
"I think he's number one in that respect. He's had a very good first year, and now he's in a top team. Talking to some of the people I know at Ferrari they've been very impressed with his approach and attitude. I think he's pretty special."
Brawn added that he believes the Italian team are in a much better position to mount a championship challenge this year. He made reference to the calmer atmosphere within the team under the leadership of Mattia Binotto.
"The team (Ferrari) was in a bit of disarray last year, with Sergio passing away and then clearly there was some friction in the team between Maurizio and Mattia, it wasn't smooth. So it wasn't an easy atmosphere last year."
Bahrain International Circuit - Winter testing