Abu Dhabi - 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.
Hamilton, chasing his second title, was 0.133 seconds quicker than Mercedes team-mate and rival Nico Rosberg with a lap of 1m43.476s on an afternoon that again saw the sport's dominant team in a class of its own.
Fernando Alonso, preparing for his last race with Ferrari, was third quickest - but a huge 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 fight for the leftovers.
Hamilton leads his German team mate by 17 points but he 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.
CAR TROUBLES
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.
Jenson Button, who could be racing for the last time in Formula One, was 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 has returned in the hope of finding a buyer to keep it on the track.
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. - Reuters
RESULTS
1 Lewis Hamilton (Britain) Mercedes - 1m43.476s
2 Nico Rosberg (Germany) Mercedes - 1:43.609
3 Fernando Alonso (Spain) Ferrari - 1:45.184
4 Sebastian Vettel (Germany) Red Bull - 1:45.334
5 Daniel Ricciardo (Australia) Red Bull - 1:45.361
6 Jean-Eric Vergne (France) Toro Rosso - 1:45.718
7 Daniil Kvyat (Russia) Toro Rosso - 1:45.835
8 Valtteri Bottas (Finland) Williams - 1:45.913
9 Sergio Perez (Mexico) Force India - 1:45.983
10 Nico Huelkenberg (Germany) Force India - 1:46.030
11 Kevin Magnussen (Denmark) McLaren - 1:46.049
12 Kimi Raikkonen (Finland) Ferrari - 1:46.131
13 Felipe Massa (Brazil) Williams - 1:46.549
14 Esteban Gutierrez (Mexico) Sauber - 1:46.556
15 Pastor Maldonado (Venezuela) Lotus - 1:46.711
16 Esteban Ocon (France) Lotus - 1:47.066
17 Jenson Button (Britain) McLaren - 1:47.235
18 Kamui Kobayashi (Japan) Caterham - 1:47.971
19 Adderly Fong (Hong Kong) Sauber - 1:48.269
20 Will Stevens (Britain) Caterham - 1:50.684