"The run after the summer was really important for me and Lewis has that run at the moment", said Rosberg, who won in Belgium, Italy and Singapore previous year after the summer break to leave Hamilton with a mountain to climb. "If we're not the best, we're certainly close and I think this circuit is another chance for us to show that and I'm looking forward to it very much".
Ferrari Formula 1 technical chief Mattia Binotto has conceded the team does not yet fully understand the engine issues that hit both its cars in last weekend's Malaysian Grand Prix.
"I think that to improve your performance you need to improve your auto and your package but as well you need to improve your organization", Binotto said.
His auto was swiftly removed and moments later team mate Vettel, who had earlier survived his own slide through the same gravel trap, jumped up to third on 1m 29.717s on the supersofts.
He said: "The fans are pretty special here - to be out there in the rain, waiting for us to go out through the whole of FP2".
"I don't know. He won't be any more aggressive than I am", said the triple champion.
"Being able to put together laps like today is the one you wait for all weekend, Q1, Q2, Q3 - motorsport is about ultimate performance from myself and the auto".
Mercedes was debating whether to run the team's latest aerodynamic package for the Japanese GP.
The Finn and team-mate Lewis Hamilton, who was just 0.014 seconds behind, both set their fastest times on the "soft" tyre, not the fastest "super-soft". On Saturday, Ferrari will run with this gearbox again, so then we will see if Ferrari will need to take a five place grid penalty or not.
"The vehicle should be a bit better in the race", said Vettel.
The 34-point lead to overhaul now stand as something of a sporting Matterhorn to overcome at this stage in proceedings, but momentum in this sport is an unpredictable beast at the best of times.
"So the main thing for me is to understand the SuperSoft performance". In the long run, that's a strength of his.
Lewis Hamilton says he is "not comfortable at all" with his position in the championship despite a sizeable lead over rival Sebastian Vettel. In Malaysia we had a problem affecting me and Kimi.
"So it was something of a blessing when we managed to get a largely dry FP1".
"Valtteri did a great job, obviously he's got the penalty at the start, but still he's got a great opportunity in the race to get up there with us".
He said: "Although that may be an unusual session, it was actually quite a good one". "We tried a lot of things and it was good to feel the power of the vehicle".