Rosberg sets pace in Valencia

Nico Rosberg and Mercedes will hope to have taken a step in the right direction following first practice ahead of Sunday's European Grand Prix.

Formula One's innovation race is now in full swing and Mercedes, along with Ferrari and Renault, have all finally caught up with Red Bull this weekend by employing a blown diffuser at the rear of the car.

The device, that aids performance by blowing exhaust gases through the diffuser, speeding up the air flow and so aiding grip, has proven particularly beneficial for Red Bull this season, notably on circuits with high-speed corners.

The 25-turn Valencia street circuit that winds its way around the port area is not that type of track as it has many slow corners, but the low-exhaust system will still provide some performance gains.

Even though McLaren will not be introducing their device until the British Grand Prix in a fortnight's time, their on-form duo in Lewis Hamilton and Jenson Button were at least in close attendance to Rosberg who led the way after the first 90-minute session.

The German, who celebrates his 25th birthday on Sunday, was fastest with a lap of one minute 41.175secs for the 5.419km track as he also deployed the team's F-duct system - that stalls the rear wing and so again assists airflow and performance - to good effect too.

Rosberg finished 0.164secs ahead of championship leader Hamilton who was a marginal 0.044secs quicker than Button.

Renault's Robert Kubica is another expected to perform well, with the Pole fourth, half a second down, and the only other driver to finish within a second of Rosberg.

Ferrari's Felipe Massa, the Red Bulls of Sebastian Vettel and Mark Webber, along with Michael Schumacher in his Mercedes were all just over a second off the pace, and all within 0.096secs of each other.

Ferrari's Fernando Alonso was ninth quickest, 1.2secs adrift, with the Williams duo of Rubens Barrichello and Nico Hulkenberg 10th and 11th, the Grove marque - like McLaren - not introducing their blown diffuser until Silverstone.

Force India test driver Paul di Resta took over Adrian Sutil's car for this session and was 16th, 2.2secs behind Rosberg, but just 0.057secs off team-mate Vitantonio Liuzzi.

The Lotus duo of Heikki Kovalainen and Jarno Trulli, with their cars sporting a '500' logo to commemorate the team's milestone of races, experienced vastly differing fortunes.

Kovalainen was 19th, only marginally slower than Jaime Alguersuari in his Toro Rosso, but Jarno Trulli, who has a new chassis this weekend, was almost three seconds down on his team-mate.

Trulli was 22nd overall, just over six seconds behind Rosberg, and fractionally ahead of Hispania Racing test driver Christian Klien and Virgin Racing's Lucas di Grassi.