Melbourne - World champion Lewis Hamilton topped the timesheets for Mercedes in both practice sessions of the Australian Grand Prix on Friday but the waterlogged conditions put a dampener on Formula One's season opener.
With intermittent showers blighting the day, the teams head into the race weekend short of set-up work and lacking valuable data on their tyres, meaning qualifying could be a lottery.
Hamilton, bidding for a third successive title with Mercedes, posted a lap of one minute 29.725 seconds in the opening session, over four-tenths of a second quicker than Red Bull's Daniil Kvyat.
But the Briton could manage only 1:38.841 in the rain-delayed second, with the track too greasy to go anywhere near full throttle.
He was nearly half a second faster than Force India's Nico Hulkenberg, with Ferrari's former world champion Kimi Raikkonen third quickest in the second session.
Hamilton's team mate Nico Rosberg, who won the final three races of last season, had a day to forget.
After posting the sixth fastest lap in the opening session, he skidded at turn six in the later practice and damaged his front wing in a collision with the barrier.
The German rolled slowly around the track for a few moments before being called to stop, as Mercedes motorsport boss Toto Wolff glared at a television screen in the garage.
Red Bull had a better day, with Kvyat's Australian team mate Daniel Ricciardo third behind the Russian in the initial run and fourth-quickest in the later session.
Four-times champion Sebastian Vettel, tipped to threaten Hamilton's ambitions of a fourth title overall, was eighth quickest in the second session after failing to post a time in the first as gusty winds buffeted the street circuit.
His team mate Raikkonen locked up and skidded at a turn in FP1 to post one of the slowest times of the session.
Toro Rosso's Carlos Sainz struggled with a reliability problem early and was unable to post a lap time in the early session but returned to record the fifth fastest in FP2.
Seven drivers, including both Williams drivers Felipe Massa and Valtteri Bottas, did not trouble the timers in FP2, with teams seeing little value in testing the car in the wet.
New team Haas, the first U.S.-owned F1 outfit in 30 years, had a cautious debut with French driver Romain Grosjean and Esteban Gutierrez posting slow times in both sessions.
2ND FREE PRACTICE
1. Lewis Hamilton (Mercedes) 1:38.841
2. Nico Huelkenberg (Germany) - Force India-Mercedes - 1:39.308
3. Kimi Raikkonen (Finland) - Ferrari - 1:39.486
4. Daniel Ricciardo (Australia) - Red Bull-TAG Heuer - 1:39.535
5. Carlos Sainz Jr (Spain) - Toro Rosso - Ferrari - 1:39.694
6. Fernando Alonso (Spain) - McLaren - 1:39.895
7. Jenson Button (Britain) - McLaren - 1:40.008
8. Sebastian Vettel (Germany) - Ferrari - 1:40.761
9. Sergio Perez (Mexico) - Force India-Mercedes - 1:41.256
10. Daniil Kvyat (Russia) - Red Bull - TAG Heuer - 1:42.411
11. Esteban Gutierrez (Mexico) - Haas-Ferrari - 1:42.891
12. Pascal Wehrlein (Germany) - Manor-Mercedes - 1:43.401
13. Romain Grosjean (France) - Haas-Ferrari - 1:43.731
14. Rio Haryanto (Indonesia) - Manor-Mercedes - 1:44.304
15. Nico Rosberg (Germany) - Mercedes - 1:47.356
16. Kevin Magnussen (Denmark) - Renault
17. Jolyon Palmer (Britain) - Renault
18. Felipe Massa (Brazil) - Williams-Mercedes
19. Valtteri Bottas (Finland) - Williams-Mercedes
1ST FREE PRACTICE
1. Lewis Hamilton (Britain) - Mercedes - 1:29.725
2. Daniil Kvyat (Russia) - Red Bull - TAG Heuer - 1:30.146
3. Daniel Ricciardo (Australia) - Red Bull-TAG Heuer - 1:30.875
4. Nico Huelkenberg (Germany) - Force India-Mercedes - 1:31.325
5. Max Verstappen (Netherlands) - Toro Rosso-Ferrari - 1:31.720
6. Nico Rosberg (Germany) - Mercedes - 1:31.814
7. Fernando Alonso (Spain) - McLaren - :33.060
8. Jenson Button (Britain) - McLaren - 1:33.129
9. Sergio Perez (Mexico) - Force India-Mercedes - 1:33.370
10. Kevin Magnussen (Denmark) - Renault - 1:34.060
11. Valtteri Bottas (Finland) - Williams-Mercedes - 1:34.550
12. Felipe Massa (Brazil) - Williams-Mercedes - 1:34.679
13. Felipe Nasr (Brazil) - Sauber-Ferrari - 1:34.796
14. Jolyon Palmer (Britain) - Renault - 1:35.477
15. Marcus Ericsson (Sweden) - Sauber-Ferrari - 1:37.956
16. Pascal Wehrlein (Germany) - Manor-Mercedes - 1:40.401
17. Kimi Raikkonen (Finland) - Ferrari - 1:40.754
18. Esteban Gutierrez (Mexico) - Haas-Ferrari - 1:41.780
19. Rio Haryanto (Indonesia) - Manor-Mercedes - 1:43.372
20. Romain Grosjean (France) - Haas-Ferrari - 1:43.443
21. Sebastian Vettel (Germany) - Ferrari
22. Carlos Sainz Jr (Spain) - Toro Rosso - Ferrari
Reuters