Williams' Felipe Massa surprisingly topped the timesheets on the first morning of Formula One's second pre-season test in Barcelona on Tuesday.
The Brazilian posted the second fastest time in five days of testing so far in 1min 19.726.
Massa, 35, had retired at the end of last season only to reverse his decision when Williams had a vacancy as Valtteri Bottas joined Mercedes.
Red Bull's promise to up their speed from last week's first test was also fulfilled as Daniel Ricciardo recorded the second fastest lap.
Three-time world champion Lewis Hamilton had a quieter morning with his 49 laps low by Mercedes own high standards in third.
Hamilton will hand over to Bottas for the afternoon session.
Meanwhile, Sebastian Vettel kept a lid on the promising pace showed by the new Ferrari last week, as he remained on slower medium tyres in posting the fourth fastest time.
At the other end of the paddock, McLaren's troubles continued as Belgian rookie Stoffel Vandoorne could only register 34 laps before more problems with the team's Honda engine halted his morning session early.