Helmut Marko expects Red Bull to make a "significant step forward" at the Spanish Grand Prix next month after a disappointing start to the Formula One season.
Daniel Ricciardo and Max Verstappen have managed just one podium finish between them in the first three races of the year.
Ferrari already hold a 55-point advantage over Red Bull in the constructors' standings, with Mercedes just three adrift of the Italian team.
Red Bull motorsport consultant Marko is confident the Milton Keynes-based team can make their presence felt after revamping the RB13.
"We have two problems: Renault had some reliability issues, which have slowed them down in the development; and we didn't deliver the chassis that we should have done," he told the official Formula One website.
"But we are working day and night to pick up our shortcomings. We are pretty optimistic that we will make a significant step forward in Barcelona where a big change of parts is coming.
"So sometimes patience is the best virtue a driver can have."
He added: "The chassis will be revamped in Barcelona and Renault is planning something for Montreal."
Marko still thinks Ricciardo and Verstappen can challenge despite a slow start.
He said: "When we fought for the championship with Sebastian [Vettel] against [Fernando] Alonso [in 2012] we were 42 points behind still after the summer break - and won. So we are the masters of catch-up."
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