JEREZ, Spain (AP) With six weeks to go before the start of the Formula One championship, the first pre-season testing session in Jerez will offer early clues as to whether any team can stop Mercedes from crushing its rivals again.
Although last season was thrilling, that was due to the rivalry within Mercedes between Lewis Hamilton and Nico Rosberg, with Hamilton sealing his second F1 title on the last day in the much-hyped double-points race in Abu Dhabi.
In the first year of the V6 turbo hybrid engines, Mercedes triumphed in 16 of 19 races and finished nearly 300 points clear in the constructors' championship. Red Bull won the other three races.
In the two months since Abu Dhabi, Red Bull, Ferrari and McLaren have been frantically trying to figure out how to close the gap.
Teams have been reshuffled, too, with four-time champion Sebastian Vettel quitting Red Bull after a miserable year to join struggling Ferrari, which saw two-time champion Fernando Alonso of Spain leaving to join a revamped and ambitious McLaren.
Energized by Alonso's arrival, using Honda engines for the first time since 1992, and with chief executive Ron Dennis back at the helm, McLaren hopes the MP4-30 car can bring back the glory days of Ayrton Senna and Alain Prost in the late 1980s.
Such aspirations are far-fetched, but a first GP win since 2012 is realistic given the highly experienced pairing of Alonso and Jenson Button, the 2009 F1 champion.
''We're prepared for a steep learning curve,'' said Alonso, who had an unhappy spell at McLaren in 2007. ''But it's clear to see that inside McLaren-Honda, there's total commitment, and a real change in feeling.''
The home fans will be cheering on the 33-year-old Alonso when the 2015 F1 cars make their track debuts Sunday in southern Spain, and he will take the start line in Melbourne on March 15 more fired up than ever.
''My motivation could not be stronger for the new season,'' said Alonso, who finished sixth last year. ''I've done a lot of training during the winter break, to reach my peak physical fitness.''
Alonso has not won a GP since winning at the Spanish GP in May 2013, and Ferrari failed to win a race last year for the first time since 1993.
Vettel has little room for error, and much will be expected of the 27-year-old German.
Ferrari will hope that the postseason break did Vettel some good because things got so bad last year at Red Bull that he even considered retiring, according to Red Bull's team principal Christian Horner.
Williams drivers Felipe Massa - the 2008 F1 runner-up - and Valtteri Bottas will be feeling confident after finishing last season strongly.
Elsewhere, all eyes will be on 17-year-old Max Verstappen as F1's youngest ever driver begins his career with Toro Rosso alongside newcomer Carlos Sainz Jr of Spain - the son of two-time rally world champion Carlos Sainz.
Daniil Kvyat has the task of replacing Vettel at Red Bull, although given his speed and confidence that is a challenge the 20-year-old Russian driver will relish.
Eight teams will take part in testing, which ends on Wednesday. Caterham and Marussia have folded and Force India won't run until the second pre-season testing session in Barcelona from Feb. 19-22.
The final session will be held a week later, also in Barcelona.