TAKING THE LEAD: Williams' driver Valterri Bottas topped the timesheets during the second day of testing. Image: AFP / Josep Lago
Barcelona, Spain - Valtteri Bottas recorded the fastest time for Williams on day two of the second pre-season test in Barcelona as double world champions Mercedes enjoyed another promising session.
Bottas posted the fifth fastest time through six days of testing and the second quickest on the supersoft compound in 1min23.261sec.
Hamilton was just over three tenths of a second back on a slower setup as he was released onto the soft tyres for the first time after piling up huge mileage in the W07.
However, the Englishman's time was six tenths of a second down on the best lap posted by Mercedes team mate Nico Rosberg on the soft tyres on Tuesday.
Hamilton and Rosberg combined for another mammoth 164-lap day with the German completing a race simulation in the afternoon, albeit with only the ninth fastest lap time on the day.
Kevin Magnussen provided more hope for Renault ahead of their return to the sport as a constructor with the third quickest time and an impressive 126 laps.
Sebastian Vettel posted Ferrari's best time of testing so far on the medium compound in fourth, whilst the Italian giants also ironed out a few reliability problems from Tuesday to post 151 laps.
There was also encouragement for McLaren-Honda as Jenson Button enjoyed a relatively trouble-free day with 121 laps.
However, Button's best time on soft tyres was 1.5 seconds down on Hamilton to again show the team have to breach to get back to the front of the grid.
American newcomers Haas had their first nightmare day as a turbo charger problem meant Esteban Gutierrez failed to even register a lap time.