Admitting that this season is a "write off", Red Bull boss calls on Renault to go for broke.

Barcelona 2014 not only marked Nico Rosberg's kick-start to his championship challenge, it also saw Daniel Ricciardo on the podium for the first time. Indeed, it was only a few weeks later that he scored his maiden F1 victory.

This year, after five races his best result is a brace of sixths, the Australian currently languishing in seventh place in the standings. Teammate Daniil Kvyat has fared even worse, a non-starter in Melbourne and forced to retire in China, the Russian is currently fifteenth in the standings, his best result being a brace of ninths.

To compound the Austrian team's problems, it is facing increasingly stiff opposition from its 'sister' team, which uses the same Renault power units, the units blamed by Red Bull for its current ills.

"It is not enjoyable being in a Grand Prix when you are just going around, you're not racing," he told reporters at the end of another difficult day. "We want to get back. The frustration is that not all of it is in our hands. We are relying on our partner."

With Ricciardo needing to dip into his engine allowance once again at the weekend, it is surely only a matter of weeks before the Australian takes his first penalty hit of the season, with his teammate sure to follow. Consequently, Horner has called on Renault to go for broke, and take some risks for fear that his team will slide further into the abyss.

"This year is pretty much of a write-off," he admitted, "you have just got to go for it, even if you end up using 20 engines. It is far easier to make a fast engine reliable than a reliable car fast.

Fifty points adrift of (third-placed) Williams, never mind Mercedes and Ferrari, Horner said: "The step we need to get on the back of that group can't be done just with the chassis. It is a positive that we got four engines to the finish... that is a step forward from previous races. Reliability has taken a step forward, so focus desperately needs to turn to performance.

"I think they know what the deficit is, the question is how are they going to make it up? That is the bit they don't know at the moment. We want it as soon as possible but Renault are nervous about reliability, so I think it will still be the second half of the year before we see anything significant."