Helmut Marko believes McLaren would be hard pressed to claim - like it did last year - that its chassis is the best on the grid given its poor performance to date.
Before the season kicked off, Fernando Alonso said the Woking-based outfit would target Red Bull Racing at the outset in 2018 as the two teams are powered by the same Renault engine.
While McLaren's level of performance has improved, its drivers are nowhere near snapping at the heels of the Milton Keynes squad's chargers.
Even worse, McLaren could not rival the pace of Toro Rosso in Bahrain, the team which took on its batch of "weak" Honda engines.
"Mr Alonso wanted to attack Red Bull but he was behind the Toro Rosso," Red Bull motorsport boss Marko told Auto Motor und Sport.
"The McLaren cannot be that great and it was not just the Honda engine that made them slow -- they are still last on the straight with the Renault," he added.
Marko, whose Red Bull outfit is considering switching from Renault to Honda for 2019, joins those who think McLaren made a strategic error late last year by ditching the Japanese manufacturer.
"They not only lost an engine that is getting better and better, they also gave up a lot of money," he said.
McLaren's Stoffel Vandoorne believes Red Bull remains a good benchmark for his team, regardless of how it has performed so far in 2018.
"No matter what engine you have in the car, you're always under pressure in Formula 1," said the Belgian.
"We have clearly identified Red Bull as a reference point so it makes sense to be compared with them.
"But we are only at the beginning of the season, so we have to wait a bit for the arrival of new parts to see exactly where we are in the hierarchy."