With 13 minutes of the final hour-long practice session remaining for the Japanese Grand Prix, Vettel was seen chatting at the back of the Red Bull garage wearing his jeans and team t-shirt.
His mechanics, meanwhile, were working on his car and changing the KERS battery after it encountered a fault.
After claiming pole at Suzuka for the last four years, and currently on a run of three successive poles this season, there is a chance the 26-year-old German may be deposed from top spot.
Vettel, on course for his fourth consecutive Formula One world title, had to settle for ninth place on the timseheet, finishing almost a second down on team-mate Mark Webber.
With the 37-year-old Australian out in front by 0.134secs to Lewis Hamilton in his Mercedes, Vettel is still favourite to make it five poles in a row at this track if all is well with his car come qualifying.
Hamilton managed to depose team-mate Nico Rosberg down to third with a flying lap in the dying seconds, with the German three tenths of a second adrift of Webber.
Romain Grosjean in his Lotus was next up, albeit with a considerable gap to Rosberg of a third of a second, followed by the Ferrari pair of Fernando Alonso and Felipe Massa.
Alonso, 77 points adrift of Vettel with only 125 available, called on Ferrari to make some gains overnight as he trailed behind the likes of Toro Rosso's Daniel Ricciardo and Jenson Button in his McLaren on Friday.
The Maranello marque appear to have done that, but at this stage not enough to get the Spaniard on the front two rows of the grid and in a position to pressurise Vettel.
Button was seventh quickest, followed by Lotus' Kimi Raikkonen, then Vettel, with Sauber's Nico Hulkenberg completing the top 10.
Force India's Paul Di Resta was down in 15th, 1.607secs back, whilst team-mate Adrian Sutil was 18th and another casualty of the track.
After a number of incidents on Friday, Sutil lost the rear of his car exiting the sweeping Spoon Curve, the German pirouetting 180 degrees before hitting a barrier and losing the front wing.
Marussia's Max Chilton was 21st and 3.791secs adrift, 3.5secs ahead of rock-bottom team-mate Jules Bianchi.
The Frenchman, however, was on a different programme as he missed all of yesterday's second session after smashing his car into a barrier at the second Degner corner.