The gap between the Mercedes pair was marginally wider than it was in first practice, with Rosberg ahead by just under four tenths of a second.
Nico Hulkenberg was seventh, ahead of Jenson button whose session was gut short due to an eye problem which saw him visit the circuit medial centre and later a local hospital just after the conclusion of the session.
Haas' Romain Grosjean split the Williams pair, while his team mate was in 16th.
Bahrain International Circuit - Winter testing
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