Red Bull believes its RB14 chassis is "absolutely ahead" of its Formula 1 rivals this year, but it does not expect that to be enough to sustain a season-long challenge.
The team made a slow start in 2017 after windtunnel problems left it on the back foot, but it believes GPS data from pre-season testing this year shows it has a car team principal Christian Horner says does not "give anything away in the corners".
Red Bull advisor Helmut Marko told Autosport: "We know that our chassis is absolutely ahead on the GPS data and so on.
"There's a problem with the engine. It is difficult to even begin to achieve the excellent Mercedes performance that has been delivered."
Horner says that the team can be optimistic heading into the start of the season, but he believes Red Bull's engine deficit to Mercedes and Ferrari will prevent it from sustaining a season-long challenge.
"It is difficult to draw too many conclusions but I don't think we give anything away in any of the corners we looked at in Barcelona," said Horner in an exclusive interview.
"And if you went out and had a look on circuit, it was evident that the car looks well poised.
"There is a real optimism about this car. It responds well. It is giving the drivers good feedback and it is a great starting point as we go into the season.
"We know where our deficiencies are to our opponents, and we just have to compensate in other areas."
Engine supplier Renault has already made clear that its focus at the start of the season will be on reliability even if that means sacrificing some performance.
When asked if he believed the chassis could overcome any power deficit, Horner said: "Over a season I don't think so.
"But there will be some circuits where we will be stronger than others.
"Our focus is on dealing with the bits that we can control, maximising our own performance, our own reliability, and grabbing opportunities when they present themselves."
Horner thinks it may not be until the Spanish GP, when Renault could choose to introduce its second power unit of the year, that the team may be in a position to get on even terms with Mercedes and Ferrari.
"The first three or four races are all very power sensitive tracks and they are going to be pretty tough for us," he said.
"It is probably not until we get back into Europe and whatever they have with engine two, that one would hope the gap will diminish.
"China/Bahrain/Australia, they are all quite big engine circuits, so we are really reliant on our colleagues in Viry coming up with something."