Lando Norris believes McLaren are "three months behind" in car development as they bid to get back to the front of Formula 1.
The reigning two-time constructors' champions already appear hard pressed to make it a hat-trick of consecutive crowns this year, given they trail leaders Mercedes - winners of seven of the season's first eight races - by 143 points.
Like all the leading teams, McLaren have regularly introduced update packages, of varying scale, to their car so far this season with two more revisions brought to the track at last weekend's Austrian Grand Prix - although the team did not use one of them, their version of Ferrari's 'Macarena' rotating rear wing.
But speaking on media day at the start of the Spielberg event, world champion Norris said overhauling their rivals was a longer process than the impact of single race upgrades.
"One good upgrade, no [is not enough]," said Norris, who is fifth in the Drivers' Championship standings.
"We need three, four, five, but it depends. Sometimes you take one little piece at a time, sometimes you try and make something so everything goes together because it's a new philosophy.
"We're like two, three months behind. That's not one upgrade; that's a lot of bits.
"I don't think we're going to be quickest anytime soon but hopefully over the next three, four, five months we can catch up and we can narrow the gap to be on pace with them."
McLaren proved their ability to make significant in-season ground during the last era of regulations and Norris added: "To catch up takes a huge effort from the team, which they're doing. Everyone is very excited and motivated because we know it's possible.
"We're like three months behind and that's a hard task to overcome but everyone in McLaren knows that we can achieve that and we're excited to try and do it."
Norris and team-mate Oscar Piastri were dominating the championship this time last year but have just two podium finishes apiece to show for the first eight weekends of the sport's new rules era this year.
Piastri finished fourth with Norris seventh last Sunday in Austria, the former ending up 21 seconds behind George Russell's race-winning Mercedes.
Speaking on Sunday night, team boss Andrea Stella said it was clear they had to improve the car.
"We know from our side that we miss probably three, four tenths of a second [a lap], and we see this in qualifying, and we see this in the race," said McLaren's team principal.
"We tend to see pretty much the same pattern across different tracks. So it's a very consistent picture, and we know exactly what we have to do. We have to upgrade the MCL40."
F1's in-season car development race is proving especially critical this year, given teams are still able to find relatively big chunks of performance time in the early months of the new ruleset.
McLaren made a big jump when they introduced sizeable changes to their car at the start of May in Miami - which proved their best race weekend so far when Norris won the sprint and harried Kimi Antonelli for victory in the grand prix - with Red Bull the latest team to make big gains thanks to a sizeable upgrade of their own in Austria.
Given that trend, Stella says it is not guaranteed Mercedes will remain the fastest car all the way through this season.
So, taking inspiration from the way Red Bull caught up with McLaren themselves last year unexpectedly to take the battle for the Drivers' Championship to the wire, Stella hopes it is his Woking outfit who emerge as the chief chasers late into the campaign this time around.
"This is a battle of development for everyone," said Stella.
"Mercedes started with an advantage of a few tenths of a second but if they don't develop their car with another substantial upgrade, I wouldn't be surprised that in the second part of the season we see another team being the fastest car.
"We have seen in Austria already with Verstappen.
"The important point will be how far ahead will Mercedes be towards the end of the season if there's another team catching up, will it still be early enough to actually catch up the points and for instance set a challenge like Verstappen set a challenge last year to us in the Drivers' Championship.
"Ultimately this is what drives our motivation we want to be that team and we want to be that driver that sets a challenge to Mercedes and to the Mercedes drivers in the championship.
"It's still a long way to go in the championship and the mission for McLaren is very clear - we want to be that team."
Next up in the 2026 Formula 1 season is the big one, a Sprint weekend at Silverstone for the British Grand Prix - live on Your Site F1 and Sky One with coverage from Thursday to Sunday's race at 3pm.
