Barcelona Test: Mercedes give a glimpse of their hand

For the first time this season Mercedes unleashed one of their drivers with the Pirelli soft tyres when Nico Rosberg had a set bolted on to his car during the morning session on the first day of the second Formula 1 preseason test, at Circuit de Barcelona-Catalunya.

The German promptly popped the W07 onto the top of the timing screens where it remained for the rest of the day with his best lap time of 1:23.022 setting the benchmark.

Williams driver Valtteri Bottas was second fastest, two tenths down on the pace setting Silver Arrows, but he used the Ultrasoft tyres to set his best time.

Ominously - for Mercedes' rivals - Rosberg was 1.7 seconds up on the next best driver who used soft compound tyres on the day which was Fernando Alonso in the McLaren who set the third best time.

Fourth fastest was Kimi Raikkonen in the Ferrari, who was best of the bunch who used Pirelli medium tyres to set their fastest laps. He was a couple of tenths up on Lewis Hamilton who took over the Mercedes cockpit, from Rosberg, for the afternoon stint whereupon he concentrated on race simulations.

The reigning world champion set his best lap time on mediums and along with his teammate they were able to mass 172 laps, substantially more than the next best on the mileage count, namely Max Verstappen who managed 144 laps solo on the day.

Splitting the Ferrari and the [Hamilton] Mercedes on the timing sheets in fifth was Daniil Kvyat in the Red Bull, the Russian's best time on soft tyres was two seconds down on the top time set using similar rubber.

Sauber had their new car running for the first time, after using a 2015 car to the first test, and Brazilian Felipe Nasr did 103 laps and ended ninth quickest.

Kevin Magnussen was tenth in the Renault, after causing a red flag at the end of the day when he came to a halt out on track with 119 laps to his credit.

Haas, with Esteban Gutierrez on duty, had a shortened day thanks to fuel system problem which curtailed their running to a mere 23 laps.

Rookie Rio Haryanto had a troublesome day with Manor, an oil leak causing him to miss out most of the morning stanza as the team repaired the problem. He went on to rack up 45 laps, but was slowest of all.