By Alan Baldwin
ABU DHABI (Reuters) - Championship leader Lewis Hamilton struck a psychological blow with the fastest time in Friday's first practice for Formula One's Abu Dhabi title decider.
The Briton, chasing his second title, was 0.133 seconds quicker than Mercedes team mate and rival Nico Rosberg with a lap of 1:43.476 on an afternoon that again saw the sport's dominant team in a class of their own.
Spaniard Fernando Alonso, preparing for his last race with Ferrari, was third quickest but a massive 1.7 seconds off Hamilton's pace.
Sunday's race is likely to reflect the title battle, with the two Mercedes drivers in a duel of their own while the rest scrap for the leftovers.
Hamilton leads his German team mate by 17 points but the Briton can take nothing for granted, with double points on offer for the first time in the sport's history and mechanical failure the biggest fear.
The 2008 champion need only finish second, however, to claim the title even if Rosberg wins.
With Mercedes on course for a record 16 wins in a single season, having already notched up an unprecedented 11 one-two finishes, that looks entirely likely barring a nightmare retirement.
Red Bull's quadruple world champion Sebastian Vettel, last year's winner, was fourth fastest as he gears up for a farewell to his team before taking Alonso's place at Ferrari.
Britain's Jenson Button, who could be racing for the last time in Formula One, was only 17th for McLaren after car troubles meant he got in only eight laps.
"Great to see @MercedesAMGF1 have got a lot of competition here in Abu Dhabi," he said sarcastically on Twitter as he watched proceedings on the television monitors. "1.7 second gap!"
Williams saw both cars of Felipe Massa and Valtteri Bottas shed bodywork in incidents that curtailed their running while the team investigated.
The first session also saw less familiar names in action, with Britain's Will Stevens slowest of all as he prepared for a race debut with administrator-run Caterham.
The team had missed the last two races and have returned in the hope of finding a buyer to keep them on the road.
Hong Kong Chinese racer Adderley Fong made his debut at a race weekend for Sauber, completing 25 laps and ending up last but one. France's Esteban Ocon was in Romain Grosjean's Lotus for the first session and was 16th fastest.
(Reporting by Alan Baldwin, editing by Toby Davis)