Niki Lauda is expecting Mercedes to maintain a "small" advantage at best over title challenger Ferrari in 2015.
The German camp has admitted that the level of Ferrari’s resurgence since 2014 was a surprise.
"They (Ferrari) have created a very big project this year," F1 legend Lauda, also the Mercedes team chairman, told Brazil’s Globo.
"We knew it would be closer, but not this quickly. I see great potential in their car," said the Austrian, "as they can still add a lot more speed yet.
"We are accelerating our development programme and trusting that we will still have an edge, however small," he added.
Lauda said Mercedes’ 2014-style of domination, where victories were spread mainly between silver-clad teammates Lewis Hamilton and Nico Rosberg, is over.
"That’s what I imagine will happen," he answered, when asked if Sebastian Vettel and Kimi Raikkonen will now make it a consistently winning quartet in 2015.
"The history of F1 is full of these examples. We have to enjoy it while we are still those tenths in front, especially in qualifying," added Lauda.
"But if we continue to deliver Lewis a winning car, he will bring us victory," he said. "As a driver, he is in a state of grace."
There will be no new Mercedes engine in Barcelona, but the W06 will feature a substantial aerodynamic upgrade for the Spanish grand prix including a front wing, a spokesman confirmed.