And of that pair, Mercedes out-lapped Ferrari to the tune of almost 300 kilometres - a race distance - over the four days in southern Spain.
Nico Rosberg even did a full grand prix simulation, complete with pitstops, while others were grappling simply to run their radically-new cars.
"There was an element of psychology in the (Mercedes) game," respected Auto Motor und Sport correspondent Michael Schmidt said.
"They wanted to demonstrate strength at a time when the great enemy Red Bull was on the floor," he mused.
Officially, Mercedes has played down any suggestion it is the early title favourite.
"For me it's too early to say who is quick," Sauber driver Adrian Sutil agreed.
But "I think the Mercedes package looks quite strong," he told Britain's Sky. "They do a lot of laps and I have a feeling they are in the front right now."
Others with Mercedes power are also happy. Sir Frank Williams' team moved from the Renault camp over the winter, and after grandees Mercedes, Ferrari and McLaren, lapped more than any other rival at Jerez with the new FW36.
"Frank Williams went to the Mercedes motor home on Thursday night to personally thank Niki Lauda and Toto Wolff," Schmidt revealed.
Sutil, however - having moved from Mercedes engines at Force India to Ferrari-powered Sauber over the winter - said Ferrari is also in good shape after Jerez.
Ferrari is also happy with its new red works chassis, the F14 T. The famous Maranello marque has struggled with its wind tunnel data in recent years, but a complete overhaul is now bearing fruit.
"The technical parameters of the F14 T, as well as the aerodynamic validation we saw on track, match our expectations and provide a solid starting point, which we must now exploit as much as possible," said team boss Stefano Domenicali.