Nico Rosberg is optimistic that Williams has made 'definite progress' as the European leg of the 2009 Formula 1 campaign gets into gear in Barcelona ahead of the Spanish Grand Prix this weekend - as he resumed his now almost customary position atop the timing screens at the end of the opening practice day.

The young German has led the way more often than not in practice this year to-date, but in qualifying and on race day Williams has fallen away from the pace, meaning that whilst Rosberg has achieved P1 no fewer than eight times out of 14 in practice, he has yet to start any higher than fourth and in Bahrain just under a fortnight ago looked at genuine risk of missing the Q3 top ten shoot-out altogether.

Worse still, the inaugural GP2 Series Champion has notched up a scant 3.5 points from the opening four 'flyaway' races of the season as the multiple former title-winners have failed to exploit the full potential of their 'double-decker' diffuser-equipped, Toyota-powered FW31 - and with their rivals catching up fast and developing split-level diffusers of their own, there are fears Williams' bolt may already have been shot. Not so, Rosberg insists.

"Today was our first run with the new aero components on the car," related the 23-year-old, sixth-fastest in the morning before improving by five spots later on, "and they all seemed to work well. They're giving us a few tenths extra per lap, so we've made definite progress.

"Everyone has brought new developments here, though, so we will see how things look in qualifying. We also ran some tyre comparisons today. It's not obvious which direction will be the right one, so strategy is going to be very important and will have a major impact on the race."

Team-mate Kazuki Nakajima has also shone sporadically in practice in the early stages of 2009, and the Japanese ace was on Rosberg's pace throughout day one under the warm Catalan sun, pipping him to fifth position by less than a hundredth of a second in the morning session and ably backing the sister car up in P2 at the close of play, just under two tenths adrift.

"We had a pretty good day," the 24-year-old underlined, "and it seems that all the updates are working well. I found it quite difficult to get enough grip with the hard tyre, though; the soft one definitely has the advantage for me. We now need to focus our attention on qualifying well tomorrow."

Following a busy day focussed on aero set-up work, fuel system checks and tyre comparisons, Williams do look to be in encouraging shape - but then much the same could have been said in Australia, Malaysia, China and Bahrain, only for the Grove-based outfit to ultimately flatter to deceive when it really mattered. This time around, acknowledges technical director Sam Michael, there can be no excuses.

"We had a normal Friday during which we carried out short runs to prepare for qualifying and long runs to prepare for the race," reported the softly-spoken Aussie. "The tyres are much closer than we had anticipated on the basis of the tests we've had here, and the hard tyres look stronger than they have at other circuits.

"We should therefore expect to see more even strategies from the teams on Sunday, rather than these unbalanced strategies that we've seen in the first four races of the year whereby people have run very short final stints."