Formula One is sometimes derided by critics as predictable, yet even the biggest skeptics may concede that the 2013 season is cloaked in uncertainty.

At the completion of the last preseason tests, reigning world champion Sebastian Vettel said: "We have never had a winter that was less conclusive than this one."

And that only describes what happened on the track, where nine different drivers topped the time sheets in the first nine sessions.

It does not take into account the off-track intrigue, with every team facing the dilemma about what resources to put into developing the 2013 cars and what to put into getting a head start on designing the radically-different 2014 cars with their V6 turbo engines.

As usual in F1, the answer to those questions will be determined by money; some teams will be able to wage war on those two fronts, others will be forced to sacrifice one for the other.

The first impact can already be seen in the 2013 designs. Red Bull, for instance, has made only minor tweaks to the 2012 model car. And who can blame them, given Vettel and the team have won the past three world titles?

"There are no huge changes," master designer Adrian Newey said. "It's very much an evolutionary car. All the principles the same as last year. The devil has very much been in the detail with this car. We've tidied up some bits that we felt could be improved on. Development is now the key through the year."

McLaren, by contrast, has overhauled its design from last year and Jenson Button acknowledged that could cost the team in the early races.

"If we started this year with last year's car with a few changes to it, and we'd developed that car into 2013, we could have started with a very good car at the first race," Button said. "But after three or four races you would realize that you're at the end of the development curve with it.

"It's a long season at 19 races. It's about being strong over the whole season, not just the first couple of races."

McLaren will go into the season-opening Australian Grand Prix in Melbourne without Lewis Hamilton for the first time since 2006. Hamilton decamped to Mercedes to partner with Nico Rosberg in the biggest driver change for the coming campaign.

Mercedes topped the times in the final preseason tests in Barcelona, raising hopes that the team could be a genuine contender in 2013. However, Hamilton knows raw lap-time data from testing is an unreliable guide to how the teams will perform during the season.

"People are talking us up at the moment, (Sebastian) Vettel and Fernando (Alonso) saying we're going to be competing for the world championship. I really don't see that happening at the moment," Hamilton said. "You've got to remember the car was more than a second off, sometimes two seconds off, last year and we've not caught two seconds up. The new teams will have put another second on this year and we've not caught up three seconds. That's just a fact.

"Hopefully by the end of the year we will have gained three seconds but definitely not at the beginning."

Bookmakers seem to share Hamilton's caution, installing him at No. 4 in most markets for the drivers' championship, behind Vettel, Alonso and Button, and just ahead of Lotus driver Kimi Raikkonen.

Alonso's prominent position is a testament not only to his superb racecraft but also the fact that Ferrari travels to Melbourne with a car that looked genuinely competitive in the preseason; a marked contrast to last year when the team was embarrassingly off the pace in the early races.

"Last year it was a very difficult winter, we were completely lost and with that car we fought for the world championship all the way to Brazil," Alonso said. "We now have a car that is responding well to what we change, a car that is doing what we expect the car to do. We know we are maybe not the quickest (yet) but the starting point or the potential of this car is there."

The man they all have to catch is Vettel, and astute observers of preseason testing gave high marks to the Red Bull's performance. While Vettel and Mark Webber did not dominate times, the Red Bull team was consistently running with heavy fuel loads and should be able to match the faster times when they get into qualifying trim in Melbourne.

For Vettel, the biggest threat to his hopes of a fourth consecutive title will be how the car handles the new Pirelli tires. Pirelli has changed the composition of the rubber for the season ahead, making it less resilient in the hope of having at least two pit stops per car in each race.

"It was extremely difficult to read some setup changes and find the direction with the car because the tires were simply not good enough," a frustrated Vettel declared at the testing in Barcelona.

The difficulty coming to terms with the tires will make the season opener all the more unpredictable, as will the presence of new drivers in new cars. Only Red Bull (Vettel and Mark Webber), Ferrari (Alonso and Felipe Massa), Lotus (Raikkonen and Romain Grosjean) and Toro Rosso (Daniel Ricciardo and Jean-Eric Vergne) retain the same driver pairings as last season.

Hamilton's replacement at McLaren is Sergio Perez, who made a strong impression at Sauber last season with three podium finishes.

Sauber has drafted in another Mexican driver in Esteban Gutierrez to replace Perez, and no doubt help retain the Telcel sponsorship. He will join Nico Hulkenberg, who has moved over from Force India.

Taking his place at Force India is former driver Adrian Sutil, who is being given an increasingly rare second chance, to partner Paul di Resta.

Pastor Maldonado returns at Williams with a new teammate in Valtteri Bottas, the latest in a long line of flying Finns to grace F1.

Caterham has two new drivers in Charles Pic — who was at Marussia last season — and Dutchman Giedo van der Garde.

Marussia's lineup was the last to be finalized, with young British driver Max Chilton joined by Jules Bianchi, the Ferrari-linked Frenchman who lost out to Sutil for the Force India seat. It was a late call-up for Bianchi after Brazil's Luiz Razia was dumped by the team before he even raced because promised sponsorship money did not materialize.

The paddock is one team lighter this season, with the Spain-based HRT dropping out after three seasons.