RED Bull Racing engineer chief Guillaume Rocquelin has admitted the verdict is out on the new RB13 after a frustrating start to the opening day of pre-season testing.
Daniel Ricciardo's Red Bull twice broke down at the the Circuit de Barcelona-Catalunya, however, the Australian believes it was simply a case of the team playing it safe so early in the season.
The 27-year-old returned to the track in the final session of day one to complete 50 laps and finish fifth on the time sheets.
Guillaume said his team's early reliability headache makes it impossible to know if the RB13 is going to be able to challenge Mercedes this year.
"Obviously we lost quite a bit of time today, which was frustrating," Guillaume told Red Bull Racing.
"That was largely a function of the issues we had - a sensor problem this morning and then a problem with the energy store later on.
"The fixes we put in place cured the issues and we should be good to go again tomorrow. Daniel managed 50 laps in the end and what we saw during that period was encouraging.
"The inevitable question you get asked on day one is 'is it quick, is it a front-runner', and I'm afraid the rather dull answer to that question is 'we'll have to wait and see'.
"It's a cliche but we won't know the real answer until Saturday in Melbourne. Until then we just have to keep our heads down, stick to the plan and the performance will come."
Ricciardo said his team's technical faults were just a case of engine manufacturer Renault playing it safe.
"I'm not worried," Ricciardo said.
"I think obviously it would have been nice to do more laps in particular, but the main issues were that it was for safety measures. So let's say that we stopped running because of some sensor things, and they were giving us some warnings.
"I guess, especially from the engine side, we are playing it a bit safe and making sure that we don't do damage on day one. That is the main thing.
"But I think for now, the last two hours we got some good running and hopefully that continues for the rest of the test. Hopefully Max (Verstappen) tomorrow does 200 laps."
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