Despite his stellar start to 2008, BMW Motorsport Director Dr Mario Theissen insists it would be 'unrealistic' to expect Robert Kubica to challenge for overall honours in Formula 1 this year, whilst backing underperforming team-mate Nick Heidfeld to rise to the challenge that lies ahead of him.

Kubica has begun the campaign in fine form indeed, taking the maiden pole position of his fledgling career in the top flight in Bahrain and finishing five of the opening six grands prix inside the top four – three of them up on the podium.

Those results have left the young Pole – still in only his second full season in motor racing's uppermost echelon – sitting pretty in fourth sport in the drivers' standings, just six points shy of leader Lewis Hamilton. Theissen was quick to stress, however, that talk of a tilt at the crown this year is somewhat premature.

“That would be unrealistic,” the German underlined when asked by news agency SID whether his impressive 23-year-old charge is now a title contender in 2008.

“We have an ambitious timetable. We want to win our first race this year, and then starting from 2009 be fighting for the title.

“Since we took over Sauber, we [have] achieved the goals we set for ourselves, and we want to keep making one step after the other.”

The 55-year-old was similarly swift to leap to the defence of the under-fire Heidfeld, whose start to the season has been every bit as frustrating as his team-mate's has been noteworthy.

The experienced German has unexpectedly been out-scored by Kubica 32-20, out-qualified six-nil and indeed last time out in Monaco failed to make the final Q3 shoot-out at all, bringing to an end BMW's proud record of consecutively getting both cars into the top ten in qualifying, stretching all the way back to the 2006 Brazilian Grand Prix 19 months earlier.

The 31-year-old's major bugbear has been an inability to get Bridgestone's new Potenza tyres up to temperature sufficiently quickly, putting him at a disadvantage for qualifying and, therefore, race day too.

“We have to do everything we can so that he can get out of this low as quickly as possible,” Theissen acknowledged. “We know what he can do, especially when he is under pressure; in these situations he can deal with it and be at his best.”