Niki Lauda has said that Mercedes have work to do to catch up with Ferrari.
Although Valtteri Bottas won in Russia, Lewis Hamilton struggled and the Brackley-based team think it is because the Ferrari is better managing the new Pirelli tyres.
"Sometimes we have a car of two parts," team chairman Lauda told Germany's Auto Motor und Sport, "with a tyre window at the front and another at the rear."
A team engineer said that although Hamilton struggled at Sochi, there has been progress in how Mercedes understand the tyres.
"Ferrari is still ahead," the engineer said, "but we are good at understanding problems and drawing conclusions. However it could take some races before we get fully on top of it, because some of the problems are probably due to the car."
Lauda tipped Hamilton to bounce back strongly this weekend in Barcelona, after a particularly bad show of form in Russia.
"Bottas was quicker because he won the race but Lewis is an outstanding talent, a world champion," said the the F1 legend.
"Bottas beat him but perhaps the next three times maybe Lewis will do that."
Hamilton trails championship leader Sebastian Vettel by 13 points heading into the Barcelona race.
