MELBOURNE, Australia - Five drivers look most likely to try to stop Sebastian Vettel, four consecutive times Formula 1 Drivers' champion, scoring a fifth. Here's how it looks...Lewis Hamilton (Mercedes)The 29-year-old Briton is the early favourite to usurp Vettel and land his second Drivers' title after showing impressive form in pre-season testing.Since leaving long-term employer McLaren, Hamilton has won in Hungary, had four podiums finishes and five poles on the way to finishing fourth in the 2013 Drivers' championship. He was F1 champion at age 23 in 2008. Through 2013 he showed plenty of speed but there were inevitable teething problems, particularly his adapting to the team's braking system.Now he will look to add consistency after topping the time sheets on the final day of testingin Bahrain in the Mercedes W05, which completed more test-sessions laps than any other car.Hamilton, regarded as the fastest driver in F1, has started 129 races since his debut in Melbourne in 2007. He has 22 wins and 31 poles.Fernando Alonso (Ferrari)Spaniard Alonso, 31, finished 155 points behind Vettel in 2013 in an inferior car but is widely respected as the sport's finest all-round driver. If Ferrari can get its cars to go, then he will challenge. He won only two races in 2013 (China and Spain) but with the arrival of fellow former F1 champion Kimi Raikkonen as team mate he's under internal as well as external pressure to produce the goods.The main questions for Alonso are how well the Ferrari team will adapt to F1's new technical requirements after a season blighted by under-performance - and how he will fare alongside Raikkonen. Alonso has the experience of 215 GP starts since making his debut in Australia in 2001 and the double Drivers' champion will be looking to add to his 32 race wins and 22 poles.Kimi Raikkonen (Ferrari)Raikkonen's switch from Lotus to Ferrari has prompted much debate about the team dynamic and his partnership with Alonso but expect 'The Iceman' to live up to his nickname and stay cool under fire.The Finn won the opening race of 2013 in Melbourne for Lotus and went on to finish fifth in the championship, despite a back injury and a row with his team over money, before his big move to Ferrari. He has a reputation for consistency in finishing among the points, which encouraged Ferrari chiefs to bring him to replace Felipe Massa and strengthen the case for a first Constructors' title since 2008.His experience and legendary calm in races are expected to test Alonso and it will be fascinating to see who emerges as Ferrari's main man in 2014. Raikkonen returns to Ferrari, for which he won the title by one point in 2007, before leaving F1 for the World Rally championship in 2010, only to return to F1 with Lotus in 2012.He will line up for his 193rd start in Melbourne and has 20 wins and 16 pole starts.Nico Rosberg (Mercedes)The super-quick German will provide a stern test for team mate Hamilton at the improving Mercedes team this year as he seeks a first Drivers' title. Rosberg was sixth in 2013 after winning twice for his team at Monacoand Silverstone, as well as podium finishes in India and Abu Dhabi.He finished 18 points behind Hamilton in 2013 and was only narrowly out-qualified 11-8 across the season as he continues to improve as a driver. If Mercedes, which finished second in 2013's Constructors' standings, can keep moving forward after a strong pre-season then Rosberg could be a real contender to emulate his father Keke, F1 champion in 1982.Rosberg, 28, has three wins and four poles so far in his F1 career and is likely to benefit from the wealth of technical experience at Mercedes this season.Jenson Button (McLaren)Button is the grid's most experienced driver and will be further invigorated under McLaren's revamped leadership, headed by arch-competitor Ron Dennis, and has a style well suited to 2014's new technical requirements. His 2009 win for Brawn makes him the last F1 champion before the Vettel era began, suffered during a dreadful 2013 when McLaren failed to land a single podium finish - their worst season since 1980.Button's experience and ability to conserve fuel and tyres will be crucial through 2014 as Dennis looks to revive a team he describes as the "Manchester United" of F1.Entering his 15th season, Button has 15 wins and eight poles from 247 races. He will be joined at McLaren by Danish rookie Kevin Magnussen.Stay with Wheels24 for the first 2014 F1 race in Australia this weekend.