SEPANG, Malaysia - Defending Formula 1 World champion Sebastian Vettel is playing catch-up in what is shaping up to be a gripping 2012 season with the next race in steamy Malaysia on March 25.Red Bull's precocious young German was never off the top of the 2011 points table as he swept to a second consecutive title and he has led the standings since November 2010, when he won a last-race showdown for his maiden championship.Now the 24-year-old has a fight on his hands to achieve only the third hat trick in F1 history because McLaren emerged from pre-season testing to dominate 2012's opening GP in Australia.LOCKED IN TUSSLEFormer champion Jenson Button thee and Vettel had a timely safety car intervention to thank as he nipped in front of McLaren's Lewis Hamilton to finish second. Red Bull's Mark Webber was fourth.Now Red Bull and McLaren - the latter’s Hamilton won the Drivers' title in 2008 - are already locked in a tussle to get the most of their cars and drivers as they size up the Malaysian GP in Sepang, one of the year's toughest races.Red Bull’s team principal Christian Horner told Autosport.com: “We saw it last year - some circuits suited different cars and different characteristics. There are circuits that will affect performance but I think the teams are very closely matched."As always, it will be a development race between now and the end of the season."Easy-going Vettel was typically nonchalant about the McLaren challenge, even after Button joked that he hoped he'd seen the last of the German's famous crook’d-finger.Vettel said: "If I remember we were pretty dominant (in Australia) in 2011 and then qualifying was just a couple of hundredths between Lewis and me – we’ll see what happens."Red Bull is assumed to have been hit hardest by a ban on blown diffusers, a system that team pioneered to channels exhaust gases to increase downforce, while both teams were taken aback by Mercedes' new drag-reducing rear wing.Gearbox problems forced Mercedes' seven-times champion Michael Schumacher out early last weekend Australia and team mate Nico Rosberg as 12th.BRUTAL HEATMeanwhile Ferrari, by consensus, was flattered by Fernando Alonso's determined drive to fifth in the unloved F2012 which stumbled in testing and has been criticised as appearing over-innovative.All teams are facing one of the year's biggest challenges at tropical Sepang, where brutal heat and humidity - frequently punctuated by torrential rain - create a demanding weekend.Sauber's Sergio Perez said: "It’s one of the most physical circuits of the season. The heat is demanding for the drivers and tyre degradation. It is not an easy circuit to race - quite technical."F1's finances are also in the spotlight after reports that officials are considering a share-market flotation as part of negotiations for a new Concorde Agreement governing how profits are shared.Free practice will be on Friday (March 23). The race, 56 laps of the 5.5km Sepang circuit near Kuala Lumpur, will start at 4pm their time, 8am GMT and 10am South African time on Sunday. Stay with Wheels24 for the Formula 1 weekend.