Dr Helmut Marko has played down reports that Renault's 2017 engine came out of the blocks with an apparent technical failure.
It emerged last week that, with the French marque taking a bold step over the winter to catch up with Mercedes, the 2017 engine broke down as Toro Rosso did its track roll-out in Italy.
Yet Red Bull Racing's Marko told Auto Bild: "We believe in Renault, and at the moment there are no problems with the engine."
However, the entire pitlane is nervous about rumours that the already-dominant Mercedes has possibly made an equally big engine step for 2017.
"What scares me the most is not the Mercedes team," Toro Rosso driver Carlos Sainz told Spanish press in Barcelona, "because it is not on our radar.
"What scares me more is that Force India and Williams could have even more power. I am convinced that in previous years we could have beaten them with the same engine, so hopefully this year we will have an engine that will allow us to fight."
Renault finished the 2016 constructors' championship in ninth place.
