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Nico Rosberg's quest to begin making headway into Lewis Hamilton's healthy championship advantage got off to a positive start as he set the pace in first free practice for the Spanish Grand Prix.
Though four seconds slower than his best time in winter testing, the German maintained a slender advantage over his championship-leading team-mate throughout the 90mins session, his eventual benchmark of 1min 26.828secs holding firm by a meagre 0.070secs as the two Mercedes' established an early advantage over the competition.
Even so, it wasn't a fault-free session for Rosberg after a mistake on entry saw him take the wrong route into the pit lane, an infraction that is now being investigated by stewards.
Beyond the closely-matched title contenders, Ferrari – complete with a reported 16 new parts on the SF15-T - gave chase in third and fourth in the order of Sebastian Vettel and Kimi Raikkonen, but would fall a full second adrift of their key rivals.
Though it is Red Bull that comes to Spain with a raft of updates on its car, sister team Toro Rosso would instead shine in the morning sun, local driver Carlos Sainz turning in the fifth best lap, just ahead of team-mate Max Verstappen.
Sporting a new, shorter nose on the RB11, Red Bull will nonetheless be pleased to see Daniil Kvyat up in seventh, if less enamoured to have Daniel Ricciardo in the garage for a prolonged period of time as his new, fourth Renault power unit cried issue early on. He eventually got back out to set the 9th best time, albeit with just 9 laps to his name.
Rounding out the top ten, Williams' Felipe Massa led fellow Brazilian Felipe Nasr, the pair split by Ricciardo.
With its bold new colour scheme, McLaren-Honda endured an indifferent start to the weekend driving the upgraded MP4-30, Fernando Alonso – who suffered a spin late in the session - and Jenson Button still down in 15th and 16th, three seconds off the ultimate pace.
Meanwhile, Susie Wolff – one of three test drivers taking part in the FP1 session – turned heads with the 14th fastest time in the Williams, 2.8secs off the lead and just behind Sauber's Raffaele Marciello and Lotus' Jolyon Palmer in 12th and 13th.