JEREZ, Spain (Reuters) - No team can be considered a favourite for this year's Formula One championship because the new V6 engines create far too much uncertainty, Red Bull principal Christian Horner said on Tuesday.
Red Bull have won the past four constructors' and drivers' championships but the regulations have changed dramatically since last year with a new V6 turbocharged engine and energy recovery systems replacing the old V8s.
"All bets are off," Horner told reporters after the presentation of his team's new RB10 car at the Jerez circuit in southern Spain.
"It's impossible to predict. I think the power unit's going to be a big element in this world championship and only time will tell.
"Reliability is going to be key, the races are going to have a different look to them as well in terms of how the drivers and teams strategically go about racing because fuel economy is going to be critical," he added.
Although 10 of the 11 teams are in Jerez for the opening pre-season test, problems with the power units meant some of them got little or no mileage on the first day.
Red Bull's quadruple champion Sebastian Vettel spent a day kicking his heels as the Renault-powered team worked to fix a problem that surfaced overnight.
Horner said it was an achievement in itself just to have a car at the track.
"It's been epic this winter, to be honest with you because the car's an awfully lot more complicated, there's probably 40 percent more drawings required to produce the car," he explained.
"When you think that we only started our crash testing 10 days ago. Others have been doing that for several months so it's been a Herculean effort by every member of the team at Milton Keynes."
Horner said the new power unit posed a 'fascinating engineering challenge', even if it had probably been introduced at the wrong time for teams facing a sharp rise in costs and a tough battle to secure sponsorship.
Red Bull have a design genius in Adrian Newey, a master of aerodynamics, but Horner indicated the rule change had taken away some of their advantage.
"This by far is the biggest challenge that we've faced, not so much aerodynamically but mechanically...the shift of emphasis is moving further from chassis to power unit," he added.
Red Bull have a changed lineup, with Australian Daniel Ricciardo, 24, graduating from sister team Toro Rosso to replace his now-departed compatriot Mark Webber alongside Vettel.
Horner suggested the ever-smiling Ricciardo could surprise a few people.
"Daniel is a very fast young racing driver and he's been selected in the same way Sebastian has been. He's a pretty cool operator and he's got tremendous natural speed," he said.
"I think he could really pose a surprise on occasion this year. It's going to take him time to settle in and develop but the underlying fact is that he's extremely fast."