Nico Rosberg set the fastest time of the week in Formula 1 testing in Bahrain, as reigning champion Red Bull suffered another torrid four days of pre-season running.
Rosberg topped the final day of the test, during which Mercedes-engined teams dominated the timesheets.
Force India's Nico Hulkenberg and McLaren's Kevin Magnussen set the pace across the first two days, before Lewis Hamilton and Rosberg each took a turn to lead the way for the works team.
Rosberg's final benchmark of 1m33.283s put him within a second of his own pole time from last year's race at the same venue.
However, the team did find a number of issues with the F1 W05 over the course of the test, showing that even the more comfortable teams are not immune to the difficulties of mastering this new formula.