Nikita Mazepin went fastest on his Mercedes debut on Wednesday as the championship leaders finished F1 2019's final in-season test on top.
Valtteri Bottas set the pace for Mercedes from Ferrari's Charles Leclerc on the first of two days of F1 Testing at Barcelona.
Ferrari head into F1's final in-season test of the year at Barcelona on Tuesday with fresh questions surrounding their 2019 car.
George Russell finished the Bahrain test on top of the timesheets for Mercedes, with Mick Schumacher sixth in the Alfa Romeo.
Max Verstappen was fastest ahead of an eye-catching Mick Schumacher for Ferrari at F1 Testing in Bahrain.
Mick Schumacher made his F1 testing debut for Ferrari on Tuesday, see the best pictures from Bahrain.
Fernando Alonso will get back behind the wheel of McLaren's F1 car at the Bahrain test which follows this weekend's grand prix.
The countdown is on as Sky Sports F1 and the Formula 1 teams gear up for the start of the 2019 season ahead of the second and final pre-season test at Barcelona.
Lewis Hamilton says Ferrari's fast start to winter testing is "to be expected" and that Mercedes will face a tough fight in 2019.
Sebastian Vettel is expecting new team-mate Charles Leclerc "to put me under pressure" at Ferrari in 2019.
Formula 1 2019 begins in earnest on Monday with the first of eight days of winter testing at Barcelona with all 10 new cars on track.
©2019 Sky UK