Mercedes are expecting to be on the back foot against Red Bull and Ferrari at this weekend's Monaco Grand Prix, team boss Toto Wolff says.
Mercedes struggled in Monaco last year and Wolff believes the slow, tight track may not suit their car again.
"We don't head to Monaco as favourites. They're Red Bull and Ferrari," he said.
"Red Bull are strong in slow corners and where straight-line speed is less important. Our job is to maximise the car's potential, whatever that may be."
But the world champion's dominant win in Barcelona was against the form of the previous three events, and his victory in Baku before that came about only after trouble hit Vettel and Hamilton's team-mate Valtteri Bottas.
Ferrari proved to have the fastest car in Bahrain, China and Azerbaijan - only in the opening race in Australia and in Spain have Mercedes had a clear advantage over the field.
Wolff said: "Our first one-two of the season in Barcelona felt great. The car was quick, looked after its tyres and both drivers were positive about the balance and handling.
"But we're not thinking about it as a turning point - the track layout, surface and conditions all suited our car and played into our hands.
"So we are staying cautious with our predictions as we head to Monaco.
"It's a circuit that gives us completely different challenges - and unique ones, too.
"Last year, it became a weekend of damage limitation when we didn't find the right set-up. It was a painful lesson from us and we are determined to show that we have learned it this year."
Ferrari dominated in Monaco last year, Vettel heading team-mate Kimi Raikkonen in a one-two.
And Red Bull are expecting to be strong around the streets of the Principality.
Daniel Ricciardo, victor in China this year, would have won in 2016 had the team not bungled a tyre stop.
And this season their car has demonstrated characteristics that should mean it is competitive in Monaco, where its Renault engines qualifying power deficit to Mercedes and Ferrari is less of a disadvantage.