F1 teams got an early taste of new wet-weather tyres on the final day of the opening pre-season test in Barcelona, while Mercedes ran into trouble for the first time in 2017.
The Circuit de Catalunya was sodden by water tanks ahead of Thursday's action, which saw cars mainly take to the track on intermediate tyres.
Lewis Hamilton was conspicuous by his absence in the morning session, an electrical fault on his Mercedes ruling him out.
It is the first chink to appear in the Silver Arrows' armour this year, with Mercedes desperate to avoid the reliability issues that dogged Hamilton for large parts of 2016.
Electrical fault kept us in the garage this morning, so I've decided with the team not to drive today as I wouldn't have learned much (1/2) pic.twitter.com/LS0Tr8aWdK-- Lewis Hamilton (@LewisHamilton) March 2, 2017
Shame not to drive but it's been a great few days. The guys have done an awesome job. Can't wait to be back in the car next week! (2/2)-- Lewis Hamilton (@LewisHamilton) March 2, 2017
Valtteri Bottas' car was fine to come out in the afternoon session and put in 68 laps.
For the second time this week, Ferrari topped the timesheets through Kimi Raikkonen, who delivered a lap of one minute 20.872 seconds in dry conditions late in the day.
Mercedes were not alone in running into trouble. Toro Rosso's Daniil Kvyat was limited to a solitary lap, while Williams did not run at all on Thursday after Lance Stroll's shunt the previous day.
Romain Grosjean put in 118 laps in the Haas, a sign of the American team's growing stability, while there was progress of sorts from McLaren as Stoffel Vandoorne registered their fastest lap of the week, although his 1:22.576 remains well off the pace being set by the frontrunners that the Woking-based squad have vowed to catch this year.