|McLaren's Hamilton sprung a surprise running Red Bull close for the fastest time in Friday practice [GALLO/GETTY]
Red Bull's Mark Webber came out on top during Friday's practice for the weekend's Spanish Grand Prix at Barcelona's Circuit de Catalunya.
Webber's recorded the quickest lap time of 1 minute, 22.470 seconds, but he only edged past McLaren rival Lewis Hamilton by 0.039 seconds, who benefited from improvements to his car after the morning session.
Teammate Sebastian Vettel, who has won three of the season's first four races coming in, was third ahead of Jenson Button of McLaren.
Ferrari was the next closest to the front two but Fernando Alonso was more than a second slower than Webber, who won here last year.
Mercedes duo and fellow Germans Nico Rosberg and Michael Schumacher were sixth and seventh fastest respectively ahead of Brazilian Felipe Massa in the second Ferrari.
Sauber driver Japanese Kamui Kobayashi was ninth quickest followed by German Nick Heidfeld of Renault.
While Red Bull enjoyed a one-two in the morning, Hamilton split the Red Bulls in the afternoon session.
McLaren have brought some significant updates to Barcelona, as have others, after a disappointing showing in Turkey and the initial signs were positive.
Webber's victory in Barcelona last year, then as now the fifth round of the season, was his first in a campaign that saw him leading the championship and challenging for the title right down to the wire.
The Australian is currently third overall, 38 points adrift of champion team mate Sebastian Vettel, but with the momentum building.
The 34-year-old has been fifth, fourth, third and second in his last four races and seemingly poised to complete the sequence on Sunday.
Championship leader Vettel was second in the morning, but more than a second slower than Webber's time of 1:25.142, and third after lunch.
Vettel, 34 points clear of Hamilton, is chasing his fourth win of the campaign after starting all the races on pole position.
Venezuelan rookie Pastor Maldonado provided the only real incident of the morning when he went off at turn 12 and was stuck in the gravel after completing just 11 laps.