Nico Rosberg drew first blood Friday in his duel with Mercedes team-mate world champion Lewis Hamilton, the 29-year-old German narrowly topping the times in opening free practice session for this weekend's Spanish Grand Prix.
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Two-time champion Hamilton, who leads this year's title race by 27 points after winning three of the opening four races of the season, was second, only 0.070 seconds off the pace, with four-time champion German Sebastian Vettel of Ferrari a further nine-tenths of a second adrift.
In Formula One terms, Rosberg's advantage was wafer-thin and Hamilton sustained only the merest of scratches as he worked through his technical programme in preparation for Sunday's race.
On a warm, sunny day at the Circuit de Catalunya in the industrialised hinterland of Barcelona, about 20 kms north-west of the city, Rosberg showed he was intent on rekindling his faltering challenge to his British team-mate.
But Ferrari, for whom Finn Kimi Raikkonen was fourth-fastest, were unable to close the performance gap despite a raft of upgrades to their car following the Bahrain Grand Prix, three weeks earlier.
Spain's new local hero Carlos Sainz, son of the former world rally champion, delighted his followers in the paltry crowd by placing fifth for Toro Rosso ahead of his teenage team-mate Dutchman Max Verstappen.
Russian Daniil Kvyat was seventh for Red Bull ahead of Brazilian Felipe Massa of Williams, Australian Daniel Ricciardo, who was delayed by problems again, in the second Red Bull and Brazilian Felipe Nasr of Sauber.
The two Toro Rosso men once again proved their potential and mettle by out-performing their counterparts at senior sibling team Red Bull on a morning of few surprises and little drama.
Both the Lotus and McLaren-Honda teams continued their struggles in a woeful start to the season with two-time champion Spaniard Fernando Alonso and his McLaren team-mate Briton Jenson Button winding up in 15th and 16th places while, for Lotus, Briton Jolyon Palmer was 13th and Venezuelan Pastor Maldonado 18th, another man to spend much of the session waiting in his team's pits garage.