After controlled race victories for the German squad in Australia and Malaysia, the Mercedes duo of Lewis Hamilton and Nico Rosberg pushed each other hard in a long wheel-to-wheel battle out the front in Bahrain.
Red Bull team boss Christian Horner said it was "the first time we saw their (Mercedes') true potential", amounting to a two second per lap advantage to the rest of the field.
He warned: "In China, Mercedes are again going to be very difficult to beat given the kilometre long straight.
"But then once we get back to Europe we need to start making inroads into them."
"You need a good engine in Bahrain," he told Austrian Servus TV, "and China will also be difficult with two long straights.
"But in places like Barcelona and Monaco, the chassis has more importance again."
Marko hailed Mercedes' advantage at present.
"Through (Mercedes') ingenuity and a much longer-term preparedness, both us and Ferrari have a lot to do to even come remotely close to them.
"This will be a process that will not be achieved by a stroke of genius," he added.
Ferrari, who alongside Mercedes and Renault is the other engine manufacturer in F1, is also pushing to improve.
The works team's Fernando Alonso, who is testing in Bahrain this week, said: "We have the resources and the potential to do it. We have a very aggressive (development) programme, which we need."
"In Bahrain it was obvious that one of the three manufacturers has a huge advantage regarding the powertrain," said chief engineer Giampaolo Dall'ara.
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