The Japanese Grand Prix weekend has begun in frustrating fashion for teams after rain at Suzuka limited running in Practice One.
Following intermittent rain throughout Thursday's media day, Friday began in similar fashion leaving the figure-of-eight track drenched for start of the weekend's running. While all drivers completed at least one installation lap in the opening stages, it wasn't until the final hour that lap times started to be seen as conditions slowly improved, before the weather deteriorated again in the closing minutes.
Only 12 of the 20 drivers clocked a lap time but the session is still likely to prove memorable for Toro Rosso rookie Carlos Sainz, who set the pace for the first time in F1.
Posting a best time on the intermediate tyres of 1:49.434, the Spaniard was half a second quicker than Red Bull's Daniil Kvyat and Mercedes' Nico Rosberg, who was fastest on the full wet.
The German completed more laps than anyone in the challenging conditions - 14 - as Mercedes pressed the latest-spec engine that had to be replaced on his W06 at Monza back into service. The team plan to use it as Rosberg's Friday engine for the remainder of the season provided it shows no lingering ill-effects on day one at Suzuka.
"One of the major things we learnt, with Nico running his old engine from Monza, is that everything seems okay so far and that is why he did a lot of laps. Other than that we were doing some start practice," Mercedes technical supremo Paddy Lowe told Sky Sports F1.
Team-mate and world championship Lewis Hamilton was a spectator in Mercedes' hospitality suite for much of the rain-hit session and completed just six laps in all to end up fifth fastest. Singapore GP victor Sebastian Vettel was fourth, with Kimi Raikkonen seventh in the sister Ferrari.
The rain meant that the wait to learn whether Mercedes will regain their position at the head of the field this weekend after their shock Singapore slump continues. The wet weather is forecast to continue during Friday, but dry conditions are predicted for qualifying and race day.
Despite drivers slipping and sliding their way around the 5.8km lap during P1, everyone managed to keep it out of the barriers, although Marcus Ericsson, Felipe Massa, Valtteri Bottas and Verstappen all had off-track moments.
Indeed, both Williams drivers had particularly hairy moments when they became the first to venture out on the intermediate tyres. Bottas had to catch his FW37 after hitting a puddle coming through Turn Two, before soon running off the road at 130R, while Massa briefly slid into the gravel at the second Degner.
Meanwhile, with the team still locked out of their hospitality unit in the paddock on Friday morning, cash-strapped Lotus completed just two laps in total with the Enstone team thought to be keen to avoid their cars picking up any damage with the outfit low on spare parts.
Practice One timesheet
1. Carlos Sainz, Toro Rosso, 1:49.434
2. Daniil Kvyat, Red Bull, 1:49.938
3. Nico Rosberg, Mercedes, 1:50.077
4. Sebastian Vettel, Ferrari, 1:50.519
5. Lewis Hamilton, Mercedes, 1:50.722
6. Max Verstappen, Toro Rosso, 1:50.940
7. Kimi Raikkonen, Ferrari, 1:51.212
8. Felipe Massa, Williams, 1:52.288
9. Marcus Ericsson, Sauber, 1:53.820
10. Valtteri Bottas, Williams, 1:53.964
11. Felipe Nasr, Sauber, 1:54.013
12. Jenson Button, McLaren, 1:55.678
13. Daniel Ricciardo, Red Bull, No time
14. Nico Hulkenberg, Force India, No time
15. Sergio Perez, Force India, No time
16. Fernando Alonso, McLaren, No time
17. Pastor Maldonado, Lotus, No time
18. Jolyon Palmer, Lotus, No time
19. Will Stevens, Manor, No time
20. Alexander Rossi, Manor, No time