Daniel Ricciardo is confident Red Bull will produce a "good car" this year but fears there are still questions about the engine Renault bring to the table.
Last year Red Bull blamed Renault for their wretched campaign, which yielded just three podium finishes and not a single race victory.
But despite cancelling their contract with the French company, Red Bull were forced to sign a new one-year deal that will see them run rebranded Renault engines.
And it is that engine that Ricciardo admits could determine how his season pans out.
"I'm not going to go in thinking we can win the title. That would be the wrong thing to do," he told Autosport.
"If it works, awesome. I think we've got the platform.
"The way the team developed the car last year, it's really proven not only the quality of people, but the motivation and the hunger still within the team.
"That's been the most promising thing: I haven't seen any doubters or anybody lose motivation. Everyone's still as hungry as ever.
"Unfortunately now it's probably always going to be dependent on which engine we have and that's going to dictate the success a little bit.
"But mechanically we can definitely build a good car for 2016.
"How good is the engine going to be? That's the question."