Nico Rosberg was fastest in light rain Friday in the first practice for Formula One's season-ending Brazilian Grand Prix.
World champion Vettel has a chance Sunday to equal Michael Schumacher's 13 victories in a year and match the record nine consecutive wins by Alberto Ascari in the 1952 and 1953 seasons.
Rosberg was timed in 1 minute, 24.781 seconds on a wet Interlagos track, edging Mercedes teammate Lewis Hamilton by 0.449. Hamilton spun early in the session. Vettel went off the track near the end, but he was third.
The rain kept most drivers from using the dry weather tires that will be used by teams in 2014. Vettel, however, was able to use them briefly.