Red Bull boss Christian Horner believes the team's design work on its RB13 was partially misled by how it interpreted Pirelli's 2017 development tyres which it tested last year.
Red Bull, along with Mercedes and Ferrari, undertook development work with mule cars for the Italian tyre supplier last year, to help the company develop its compounds for the 2017 new-spec cars.
The Milton Keynes-based outfit drew upon the knowledge it gained to set a direction for its RB13, which proved somewhat wrong.
"Obviously the regulation change was reasonably significant over the winter, and I think actually running the Pirelli mule car hurt us in a few ways," Horner told Motorsport.com's GP Gazette.
"A few things changed late in with the tyres that we potentially were designing the car around. I think that may have perhaps influenced our development direction.
"I wouldn't say it backfired, but it definitely led us in a direction that wasn't conducive to the tyres that were ultimately nominated.
"The simple facts are that Mercedes and Ferrari did a better job of interpreting those regulations than we did over the winter. We then found ourselves on the back foot in winter testing."
Power unit issues which emerged during pre-season testing limited Red Bull's running compared to its rivals, compounding its problems.
But Horner believes the team is gradually putting itself back on the right path, introducing revisions in Barcelona which helped it reduce the gap to the frontrunners.
"We know the areas of weakness, and it's then addressing those weaknesses. I think that's half the battle in many respects," Horner added.
"We've got a very capable group of people that have demonstrated what their potential is with previous cars, and I've got no doubt that they will sort this car out.
"You obviously get into diminishing returns. But we definitely closed the gap in Barcelona, and we're going in the right direction.
"I believe the second half of the season for us will be far more competitive than the first."
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