"Mercedes and Williams look very strong," agreed German driver Nico Hulkenberg, whose similarly Mercedes-powered Force India team has also impressed in winter testing.
"They're standing out. McLaren is also fast," he told Germany's Auto Motor und Sport. "At the moment, the Mercedes teams are a bit in front."
Mercedes' three customer teams - McLaren, Williams and Force India - appear to have hit the jackpot with clearly the best turbo V6 'power unit' in F1's new greener era.
"At the moment that's right," Hulkenberg admitted, "but we all know how long a Formula One season is. Let's wait and see.
"On the last day (in Bahrain) Ferrari did a strong laptime, and (Daniel) Ricciardo has also done a 1.35 in the Red Bull.
"I'm assuming Red Bull will solve the problems sooner or later," he said.
Williams, ninth of the eleven teams last year, has emerged as the surprise dark horse for 2014, having switched over the winter to Mercedes power.
"They (Williams) have never had problems in the tests, have always been fast, although not quite as fast as Mercedes," Red Bull's Dr Helmut Marko told Austrian Servus TV.
Mercedes F1 chairman Niki Lauda said it is possible the German squad's works team might be pushed by its British customer in 2014.
"It (Williams beating Mercedes) can happen," said the great triple world champion.
"Our customers are very important for us, and if they can beat us, this is also good motivation and a very constructive competition," added Lauda.
According to Ferrari president Luca di Montezemolo, however - whose Maranello squad has had a conspicuously low-profile winter - it is too soon to predict the outcome of the Melbourne race in just over a week.
"Let's see how many cars get to the finish of the first race," he is quoted at the Geneva motor show by Italy's La Gazzetta dello Sport.
Indeed, it is rumoured Ferrari has been focused most specifically on reliability during the winter, and still has some performance to unfurl for the actual races.
"We are careful," Mercedes' Toto Wolff told the APA news agency, "as some teams have not fully revealed the potential of their cars.
"I have no doubt Red Bull and Ferrari will be strong contenders," he added. "Force India and Williams are also fast enough to win races.
"It will be interesting!" added Wolff.