Christian Horner believes Formula One's regulation changes and bigger cars for 2017 caused correlation problems with Red Bull's windtunnel which set the team's programme back by around two months.
Red Bull -- renowned for its strengths in aerodynamics -- was tipped to become Mercedes' direct competition for the 2017 championship following F1's new regulation overhaul ahead of the season, though it failed to crack the aerodynamic-led changes and instead lagged behind Mercedes and Ferrari from winter testing.
The quadruple world champions fell well short of its main rivals in the opening races of the year as it soon transpired the team would be unable to mount its first title challenge since 2013. Team principal Horner says the issues began in Red Bull's windtunnel, with parts that had been predicted to work when simulated at the team's Milton Keynes factory not performing once they hit the track.
"I think coming into the season we came in on the back foot really," Horner explained. "Our tools weren't correlating with what we were seeing on the track. Really it was around the Melbourne time that we identified where the issue was and then to unravel that situation and focus on developing the car, relying on the results that we were getting.
"Predominantly it was the wind tunnel that was leading us a little bit astray. I think the size of the model, the size of the tyres in the tunnel we have, gave some spurious results, whereas previous it had been very reliable in specific areas. Suddenly we had this divergence between track, tunnel and CFD.
"It probably cost us about two months," he added. "About two and a half months in terms of where it put us back to. Then of course you are working flat out to try and recoup all that time. It's not like the others are all standing still."
Red Bull claimed a somewhat fortunate win in Baku and has taken five other podium finishes, but heads into the second half of the season 173 points adrift of reigning champions Mercedes, which leads the constructors' standings. Despite the sluggish start, Horner remains optimistic that his team's recent progress can be carried into the remaining nine races of the campaign.
"Ever since Barcelona, each grand prix we've managed to get more and more performance onto the car. I think we have made good progress during the first half of the year. We lost a lot of ground earlier on but we're hoping for a much more competitive second half of the season."