Nico Rosberg thinks Mercedes' utter dominance of the 'power unit' era may finally be over.
Before retiring, Rosberg won the 2016 title for the German team. And since 2014, when the turbo V6 era began, Lewis Hamilton has won every other championship.
"This year, everything resets to zero because of the rule changes," Rosberg told DPA news agency.
"Perhaps Mercedes will no longer be the dominant force. I'm really looking forward to seeing that," he said.
"Of course the pressure is very big," he said.
"They have now had two chances and last year in particular they didn't use them," Rosberg said of Ferrari and Vettel.
And putting extra pressure on Vettel is the arrival of his new young teammate, Charles Leclerc.
"I am sure we will have a lot of fun, because the boy is really on the gas," said Rosberg.
"He is on a different level to Kimi, who was clearly number 2. Leclerc goes straight to number 1 and it will to exciting to see how Sebastian deals with it."
Rosberg also thinks Valtteri Bottas has a chance to bounce back in 2019, after being comprehensively beaten and demoralised by Hamilton last season.
"If he has a good start and Lewis loses some of his motivation, which sometimes happens to him, a lot can change," he said.