Lewis Hamilton led a Mercedes one-two in Spanish Grand Prix practice yesterday while Red Bull's world champion Sebastian Vettel was sidelined for most of the two sessions by an electrical problem.
Race favourite Hamilton was quickest in both, 0.449 of a second faster than championship-leading teammate Nico Rosberg in the afternoon and 0.868 ahead of McLaren's Jenson Button in the morning.
While Hamilton pounded out the laps, ahead of a weekend that could bring him a fourth successive win, four-time world champion Vettel was little more than a spectator at the Circuit de Catalunya.
The German, winner of nine races in a row at the end of last season, was forced to park up by the side of the track early in the day with just four laps completed.
Circuit de Catalunya marshals handed him a fire extinguisher as he inspected the car before hitching a ride back to the paddock on a scooter.
Red Bull have given the 26-year-old a car built on a different chassis to the one he has used so far in what has been a difficult start to the season, but there was no obvious improvement.
"Due to an electrical problem that has damaged the wiring loom of Car No. 1, Sebastian will not be able to take part in FP2 (second practice)," Red Bull said before the afternoon session started.
"The Team will use the time to fix it to be ready for FP3 (the final session before qualifying) tomorrow."