Nico Rosberg says his Mercedes team expect to be caught by Red Bull, despite their performance advantage.
Mercedes have taken a win and two pole positions in the two race weekends so far ahead of the Malaysian Grand Prix.
Asked if Sebastian Vettel's second place on the grid in Malaysia was a "warning signal", Rosberg said: "They don't need to send warning signals.
"We expect them already. They are still the absolute benchmark in this sport. We expect them to close the gap."
Mercedes are believed by their rivals to have an advantage of about a second a lap over the next fastest car, which appears to be the Red Bull at this early stage.
Vettel won the last nine races in a row last season on his way to his fourth consecutive title.
Red Bull team principal Christian Horner says his team are losing a second a lap on the straights as a result of the power deficit of their Renault engine compared to the Mercedes, following the introduction of new turbo hybrid engines this season.
The wet weather in Malaysia on Saturday nullified some of that advantage and allowed Vettel to set a time just 0.055secs adrift of Mercedes driver Lewis Hamilton's pole position. Rosberg, who won the first race of the season in Australia two weeks ago, qualified third.
Hamilton, who was also on pole in Melbourne, said: "It's clear they have a good car. We've done a better job to close up to what Red Bull had.
"We just need to keep pushing and developing. I believe we can do that at least at the same rate as everyone else.
"It's always easier in life to chase than stay out front. I don't doubt other people will be pushing to close the gap but we'll be pushing to increase it."
Mercedes executive director (business) Toto Wolff said: "We should be under no illusion; these guys have won four world championships and they will bounce back. We just need to stay humble and keep on with the development in order not to be overtaken."
Wolff said the difference between the two cars was more complex than saying the Red Bull was making up for its power deficit with extra downforce.
"If you look at the middle sector of the lap, which requires a lot of downforce, it wasn't Sebastian's quickest sector," he said.
"We were quickest there. It comes down to driveability - less power is maybe better in that case - torque, downforce.
"For sure we have an advantage with our engine but in the wet we can't use that exiting the corners, because we don't have enough grip."