Nico Rosberg was angry after Sunday's Chinese Grand Prix, according to German media reports.
The 25-year-old hailed such a "big step" for the W02 car in Shanghai that he spent time leading the race.
But he was then told on the radio to slow down to save fuel, and finished fifth.
"The win would have been possible," Bild newspaper quoted the 'angry' Rosberg as saying.
Niki Lauda said he understands the German's frustration.
"If you have to save fuel, you are no longer competing with the others," said the triple world champion.
If you have to save fuel, you are no longer competing with the others
Mercedes competition director Norbert Haug agreed: "I can understand Nico's disappointment."
Explaining the mistake, he added: "When your car is going faster than before, it uses more fuel than before."