Dr Helmut Marko has said that McLaren's 2018 car is obviously "not great".
The British team went into Bahrain targeting the top three teams, but was ultimately outpaced even by the newly Honda-powered Red Bull junior team Toro Rosso.
"Mr [Fernando] Alonso wanted to attack Red Bull but he was behind the Toro Rosso," Marko is quoted as saying by 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."
Marko, whose Red Bull outfit is considering switching from Renault to Honda for 2019, therefore joins those who think that McLaren made a strategic error late last year.
"They not only lost an engine that is getting better and better, they also gave up a lot of money," he said.
Given that they share a Renault engine, the rivalry between McLaren and Red Bull this year is obvious.
McLaren driver Stoffel Vandoorne told France's Auto Hebdo: "No matter what engine you have in the car, you're always under pressure in Formula 1.
"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."
McLaren are third in the constructors' championship after the first two races of the season.
