Lewis Hamilton and George Russell will have to wait until the sixth race of the Formula One season at Imola in May for any major upgrades to their cars, team boss Toto Wolff said on Friday.
The former champions are third overall after two races, level on points with Aston Martin and 49 behind leaders Red Bull.
"We are doing good steps, good developments but you have to run them, confirm them, produce them," the Austrian told Sky Sports F1 at the Australian Grand Prix in Melbourne.
"So I think we are not looking for introduction before Imola. We want to do it right.
"We shouldn't expect a miracle. The next three races we won't be adding any performance. It's finding the best set-up solutions, tyre, in the right window."
Azerbaijan on April 30 follows on from Melbourne, the long gap due to the cancellation of the Chinese Grand Prix, with Miami on May 7.
Italy's Imola hosts the Emilia-Romagna Grand Prix on May 21.
Wolff said after the March 19 Saudi Arabian Grand Prix that Mercedes were "storming full steam ahead" after going back to the drawing board with their car. Read full story.
"The kind of gains that are coming in, in our R&D and in aero, are much bigger than we've had over a long time," he told reporters in Jeddah.
Seven-times world champion Hamilton said in Jeddah that champions Red Bull probably enjoyed a one and a half second advantage per lap.