Max Verstappen said Thursday that Red Bull were "not the quickest at the moment" ahead of the season-opening Australian Grand Prix, but warned it could change as the campaign progresses.
The Dutchman claimed his fourth straight world title in Las Vegas in November with two races to spare.
The 27-year-old is now bidding to join an even more exclusive club with only Michael Schumacher winning five championships in a row.
But while he won the 2024 title by 63 points from Lando Norris, he needed to overcome a mid-season run of 10 races without a win as the McLaren star pushed him hard.
McLaren and its drivers, Norris and Oscar Piastri, are seen as an even bigger threat this year, with Verstappen failing to set the fastest time of any of the winter test days in Bahrain.
Red Bull have had two weeks to analyze the data and tweak their set-ups ahead of the green light on first practice in Melbourne on Friday.
Asked how he rated Red Bull currently, Verstappen replied: "Positive shape, I guess."
But he added: "I don't know. I guess we'll find out more this weekend and after.
"We'll try to do our best. There's not really much more that we can do. Testing is not many days so we found a few areas we can work on and that's what we’ll continue to do."
According to AFP, Verstappen acknowledged there had been improvements to his car in the off-season but said it was too soon to know how it compared to McLaren, Ferrari and Mercedes.
"Impossible to know at the moment. I mean, I know that we are not the quickest at the moment, but again, it's a very long season," he said.
"If you would have asked that question here last year, and then at the end of the season, again, you know, it looked completely different.
"So a lot of things can always change quite quickly."
Verstappen won seven of the opening 10 races last year to set him on his way, before the mid-season slump opened the door to his rivals.
Matching Schumacher with five straight titles would thrust Verstappen among the all-time greats, but it is not something he wants to think about.
Instead, he prefers to take it race-by-race.
"It's actually way more relaxing to just go into it, trust the people around you, and go from there, you know," he said.
"Work hard on and off track, try to address things that you don't like in a car or whatever, and then always try to do the best on track yourself, try to minimize mistakes and keep scoring points.
