Australian Daniel Ricciardo finished seventh in the Spanish Grand Prix while Russian Daniil Kvyat was 10th but both were lapped.
The performance gap with Mercedes also appeared to have widened, even if all of the Renault-engined cars finished the race for a change.
“I think it is a positive that we got four engines to the finish without any white smoke, so it’s a step forward from where we have been in previous races,” said team principal Christian Horner.
“Reliability seems to have been a step forward, so the focus desperately needs to turn to performance before too long.”
Horner said Renault knew what the deficit was to Mercedes but were nervous about pushing too hard and compromising reliability.
The Briton said it could be the second half of the year before any significant developments emerged and the team, who won four drivers’ and constructors’ championships in a row with Renault until last year, wanted that to speed up.
“I think we are so far on the back foot with reliability anyway that, to be honest with you, this year is pretty much a write-off. You have just got to go for it, even if you end up using 20 engines,” said Horner.
“It would be better to learn and make progress in preparation for next year than be conservative. It is far easier to make a fast engine reliable than it is to make a reliable car fast. Our philosophy has always been to push performance.
“It is not enjoyable being in a grand prix like today when you are just going around, you’re not really racing,” he added. “The determination is to get back. The frustration we have is that not all of it is in our hands.”
Asked whether he was also writing off Red Bull’s chances of winning a race this season, Horner indicated that was not something he was even thinking about.
“I think we are nowhere near winning a grand prix,” he said. “You could see we got lapped today. It’s better to focus on getting performance because we are on the back foot anyway.
“You’ve got nothing to lose by throwing caution to the wind.”
(Reporting by Alan Baldwin, editing by Ken Ferris)