Mercedes are concerned that Ferrari could have the upper hand this weekend in Monaco.
Lewis Hamilton actually returned to the top step of the podium in Barcelona, but that circuit particularly suited the specifications of Mercedes's 2017 car.
Monaco, the tight and twisty street circuit, could be a different matter.
"A car with the longest wheelbase on a track with so many slow corners ... we could be slower than them," Valtteri Bottas, referring to Mercedes's battle with Ferrari this year, is quoted as saying by Brazil's Globo.
Mercedes team chairman Niki Lauda told Swiss newspaper Blick: "At the moment, Ferrari has certain advantages there.
"We will have our problems with our longest wheelbase through the tight corners. It will be even worse than in Singapore."
Mercedes currently lead Ferrari by eight points.
