Indeed, Rosberg's best lap of the race was set on lap 19, with a still relatively high fuel load, while most of his rivals had their best pace in the last 20 laps, with lighter tanks.
Red Bull team boss Christian Horner suspects: "I think Mercedes were simply maintaining a pace without pushing hard.
"Probably they have some more tricks up their sleeve, so we have a lot of work to do," he is quoted by Italy's Tuttosport.
Horner said he thinks Red Bull is currently in a group behind Mercedes that also includes McLaren and Ferrari.
And he thinks Williams has the edge on that group.
"I'm sure they did not give their best and that they are at least second best at the moment."
It is clear that Red Bull's biggest handicap is with its Renault powertrain.
"90 per cent of the problems are associated with the software and how the ERS and the engine work together," Horner is quoted by Germany's Sport1.
Daniel Ricciardo, although disqualified, finished second behind Rosberg in Australia, but Horner doubts Red Bull is ready to challenge for outright wins.
"The break after Australia is just too short (to win in Malaysia)," he said.
Worse still for Mercedes' rivals is that the Brackley based team is not resting on its laurels.
The team took an updated front wing to Melbourne but decided not to use it.
"We only had two, and we didn't want to risk damaging one and then running one car with the new wing and one with the old wing," said Mercedes designer Aldo Costa.
The other issue is that the new, radically-short nose that goes with the new wing design reportedly failed the mandatory FIA crash test.