Red Bull Racing team principal Christian Horner says that Mercedes cannot be discounted from the list of potential threats this season, especially now that it has Lewis Hamilton on board.

Speaking to the media earlier this week, Horner claimed that, while the pre-season testing programme had gone relatively smoothly for his operation, little could be read into the results, and that qualifying in Melbourne next weekend would be the first true barometer of power.

With Red Bull only topping the times on one day of the twelve spent preparing in Spain, the door was left open for others to take some of the glory, with Ferrari McLaren, Lotus and Mercedes all basking in the spotlight at various points. While the first three names would have been expected at the top of the timesheets after their 2012 seasons, Mercedes' rise was a little less predictable, but both Hamilton and team-mate Nico Rosberg posted marks that proved more than competitive.

After a dismal end to 2012, when it took just one points finish in the last seven races, Mercedes has undergone something of a shake-up, with Niki Lauda and Toto Wolff bolstering the management and Hamilton being drafted in in place of seven-time world champion Michael Schumacher. Testing did not get off to the most auspicious of starts, with both drivers suffering a lack of mileage on the first two days at Jerez, but has picked up since, and Horner - who was visited by a job-seeking Hamilton during the 2011 Canadian GP - has no doubt that the Briton's arrival has played a part.

"Mercedes have recorded some head-turning times with the programme they have been operating to, their car looks quick and, with Lewis joining the team, they will naturally take a step forward," he said, "Lewis, as we all know, is a world-class driver, and he is going to raise their level. He is worth lap time, which is why they signed him.

"I'm sure they're going to be a factor this season. Their challenge will be sustaining it over the whole season as they've been quick [at the beginning of] the last couple of years."

Sustainability will be a key for each of the eleven teams if they want to be successful, according to Horner, with development expected to continue for the frontrunners throughout the campaign, despite the focus needing to fall on the new rulebook being introduced for 2014.

"It's been a positive pre-season for us, [but] it's only when we get to Melbourne [that] we'll see everybody do their bit on Saturday afternoon, and we'll have the first glimpse of what the pecking order is. But this year is going to be a massive development race from Melbourne to Brazil."