Nico Rosberg completed a practice double at the Bahrain Grand Prix on Friday as Mercedes dominated and there was gloom for Ferrari's Sebastian Vettel under the lights.
Rosberg is eyeing a fifth consecutive victory this weekend after maintaining the momentum he build at the end of last season by winning the opening race of 2016 in Melbourne last month.
And the German laid down a marker in Sakhir, topping the timesheets from Lewis Hamilton in the first session and also having the edge on his team-mate in FP2.
Rosberg clocked a quickest lap of one minute, 31.001 seconds on soft tyres, with Hamilton 0.241secs slower in an eventful evening session in the desert.
Ferrari have plenty to ponder heading into the weekend after Vettel was left pushing his car late in FP2 before it was towed away, with the four-time world champion stating that the rear-left wheel was loose but later adding that the team are not totally sure what the problem was.
Vettel had already made a mistake on new super-soft tyres and finished sixth in the final session of the day, with team-mate Kimi Raikkonen fifth - 1.451secs off Rosberg - behind Toro Rosso's Max Verstappen.
There was plenty of encouragement for Jenson Button, who ended the day on a high note by recording the third-fastest time as the McLaren driver was 1.280secs back from Rosberg.
Romain Grosjean endured lost the front wing on Haas as he was 14th, while debutant Stoffel Vandoorne was 11th in FP2 for McLaren after being drafted in to replace the injured Fernando Alonso.
1. Nico Rosberg (Mercedes) 1:31.001
2. Lewis Hamilton (Mercedes) 1:31.242
3. Jenson Button (McLaren) 1:32.281
4. Max Verstappen (Toro Rosso) 1:32.406
5. Kimi Raikkonen (Ferrari) 1:32.452
6. Sebastian Vettel (Ferrari) 1:32.650
7. Daniil Kvyat (Red Bull) 1:32.703
8. Valtteri Bottas (Williams) 1:32.792
9. Daniel Ricciardo (Red Bull) 1:32.870
10. Felipe Massa (Williams) 1:32.873