Top 6 of today's free practice result were claimed by Mercedes-powered teams.
From start to checkered flag it was a question of which Mercedes-Powered driver was fastest on track.
Sauber's Adrian Sutil, and Caterham's Ericsson were first to hit the Sakhir circuit, then the Lotus drivers joined them on track. Lotus and Caterham were struggling with low grip in turns on medium tires, their efforts enough to set P18 and P20 for Lotus while Caterham's Kamui Kobayashi was the fastest of them placing himself 16th, right behind both Saubers.
The first of Mercedes-powered cars to set a time was McLaren's rookie sensation Kevin Magnussen with the 5th fastest result of 1:39.585 on prime tires, and 1:36.822 by the end of FP3 using options.
But then Hamilton went out attacking the top of the timesheet with a lap of 1.37.340 and two other Mercedes-powered cars behind. Jenson Button, who will become the youngest driver to reach 250 GP's in his career this weekend, slower by 0.957 and Nico Hulkenberg 1.082 behind.
With a half hour left, Sergio Perez found a rhythm and posted the 5th best time, but next lap Rosberg did his attempt and lowered all by one position setting 1:37.252 - 0,088 faster than his teammate. Sahara Force India had a very good pace in today's practice, with Perez finishing the session in 3rd place only 0.544 slower than the leader.
So the third free practice hasn't surprised us - Mercedes are the main contenders for a first starting row of Bahrain grid.
Seemed like the Red Bull drivers were working on their programs, as they were only 9th and 10th with 25 minutes remaining.
Williams drivers were the last to post a time - and the first of Massa's attempt set him on a 3rd row of the timesheets but then Valtteri Bottas lowered him by one position claiming a time of 1.38.124 just 0.01 faster then Felipe. Bottas and Massa got 4th and 5th places on softs with Button behind in 6th after he managed to do a lap in 1.36.394.
So with 20 minutes of the session left, Mercedes-powered teams were dominating the timesheet with only Renault's Kvyat in 7th.
Sebastian Vettel lost his car catching a curb in the exit of a turn 2 and spun into the gravel. He never runned on softs and ended in a P21
Drivers began to use soft tires and Hamilton posted a lap of 1.35.324 with his teammate 0.115 behind. Hulkenberg and Ricciardo were in 3rd and 4th with times of 1.36.455 and 1.37.119 respectively. This years leaders were again much faster using more softer compound then others.
With only five minutes left, Ferrari drivers used their chance to do a fast lap on soft tires, and got into the top 10 ending FP3 in 7th for Fernando Alonso and 10th for his teammate Kimi Raikkonen.
Today's qualifying will be held under floodlights as will the race on Sunday.