Red Bull have admitted they’re wary of a renewed challenge from their rivals as Sebastian Vettel unleashes his bid for a historic hat-trick of Formula One titles at this weekend’s Australian Grand Prix.

Team chief Christian Horner said Red Bull, who have dominated the past two seasons but may be disadvantaged by a key rule-change, were keen to find out the “pecking order” as the season starts in Melbourne.

“We’ve managed to tick most of the boxes that we wanted,” Horner said.

“Of course, you never know what your opponents are up to and there’s quite a bit of gamesmanship that goes on at this time of year. But we’ll soon know where the pecking order is.”

Pre-season testing in Europe, as well as exposing Ferrari’s frailties, has indicated greater competitiveness from McLaren, Renault and Mercedes, prompting observers to predict a much tighter series than last year’s Red Bull parade.

In 2011, Vettel swept to 11 wins in 19 races plus 15 pole positions, as he became Formula One’s youngest back-to-back champion and Red Bull locked up the drivers’ and constructors’ titles with three grands prix to spare.

Now the 24-year-old German stands on the threshold of joining the legendary Juan Manuel Fangio and Michael Schumacher as only the third driver to win three or more F1 championships in a row.

Red Bull’s success has been driven by their technical innovations but along with other teams they will have to operate without their pioneering, but now banned, “blown diffuser” which used exhaust fumes to create greater downforce.

McLaren chief Martin Whitmarsh set the tone this week when he said although his team, spearheaded by British ex-champions Jenson Button and Lewis Hamilton, did not look dominant, neither did any of the others.

“The bad news is we don’t look dominant,” he said.

“But the good news is that no-one else does either. I sense that we are competitive. The car seems reliable. The drivers like it and they seem to be quite buoyant.”

Whitmarsh added he was sure Hamilton would bounce back from a roller-coaster 2011, which was blighted by personal problems including a split from his pop-star girlfriend.

“He has exceptionally high standards and he won three races last year, but that’s not what he expects of himself,” Whitmarsh said.

“When you have a season that falls below your high expectations, I think you would, as a professional athlete, reconsider every aspect of your life and how you do that better.

“I think you can see that he’s definitely focused on beating one, his team-mate, and two, everyone else this time.”

Ferrari downbeat

Hamilton also refused to bite after Horner suggested that his team-mate Button, considered the slower of the two drivers, would be Vettel’s main rival this season.

“It’s the first time I’ve heard of (Horner’s remarks) but they definitely don’t wind me up,” the 2007 champion said.

Ferrari have warned they may face further problems this season and they left the final testing session in Barcelona tight-lipped after cancelling their drivers’ media sessions.

On arrival in Melbourne, which will host the season-opener on its inner-city Albert Park circuit, two-time champion Fernando Alonso struck a downbeat note for fans of the celebrated Italian marque.

“I think it is going to be difficult for us at this part of the season – we have a lot of work to do,” the Spaniard said.

Vettel, Button, Hamilton and Alonso are among six Formula One champions lining up this year, along with Mercedes’s Schumacher and Finland’s Kimi Raik-konen, who is returning to the sport with Lotus-Renault.

However, Vettel’s team-mate Mark Webber, who has added Australian markings to his helmet, admitted he is super-motivated for Melbourne after never placing higher than fifth at his home race.

“There is something extra-special to win on your home soil, but it is something that not a lot of drivers manage to do,” he said.

“I know I’ve got a good chance in our car this year so let’s see what happens.”

2012 race calendar

March 18, Australian GP
Albert Park, Melbourne

March 25, Malaysian GP
Sepang

April 15, Chinese GP
Shanghai

April 22, Bahrain GP
Sakhir

May 13, Spanish GP
Circuit de Catalunya, Barcelona

May 27, Monaco GP
Monte Carlo

June 10, Canadian GP
Montreal

June 24, European GP
Valencia, Spain

July 8, British GP
Silverstone

July 22, German GP
Hockenheim

July 29, Hungarian GP
Budapest

September 2, Belgian GP
Spa-Francorchamps

September 9, Italian GP
Monza

September 23, Singapore GP
Singapore

October 7, Japanese GP
Suzuka

October 14, South Korean GP
Yeongam

October 28, Indian GP
New Delhi

November 4, Abu Dhabi GP
Yas Marina

November 18, USA GP
Austin

November 25, Brazilian GP
Interlagos, Sao Paulo