Nico Rosberg has confessed that he fears his third place in the British Grand Prix at Silverstone eight weeks ago may well have been his final appearance up on the podium in F1 2010 - as Mercedes Grand Prix grapples to get to grips with its recent upgrades and increasingly switches its focus onto next year.

Mercedes has tallied a mere three podium finishes this season - all courtesy of Rosberg - as its title defence has not so much fallen chronically short of expectations as simply fallen flat. Having begun the campaign capable of taking the fight to the likes of Ferrari and McLaren-Mercedes on occasion, the Brackley-based outfit's disappointing MGP W01 has since slipped behind Renault on pure performance terms and into the clutches of the baying midfield pack.

The son of 1982 F1 World Champion Keke Rosberg has now conceded that he is unlikely to reach such heady heights again on merit - acknowledging that unpredictable weather conditions or attrition represent the team's best chances of regaining the rostrum over the remaining six grands prix.

"It's definitely becoming more-and-more difficult," reflected the 25-year-old German, quoted by ITV-F1. "[On] pure pace we're going to struggle to get a podium I think, but the team is continuing to work and we are still bringing improvements - a lot of them also because we need to try and get them to work properly for next year, which is also important. It helps this year and next year.

"There are always going to be opportunities, though. We have some great races coming up; there's tracks like Singapore where there's always going to be exciting races and a lot of things can happen, so [the podium] is still a possibility, definitely."

Team principal Ross Brawn has confirmed that some of Mercedes' recent issues have been caused by overheating problems as a result of its complicated new exhaust-blown rear end that was first seen in Valencia in late June - troubles that persisted all the way through to Spa-Francorchamps last weekend.

On the positive side, the Englishman admits that the team's F-duct yielded 'pretty reasonable' results in Belgium, but corroborated that whilst some further improvements are still in the pipeline between now and season's end, the lion's share of the development work is targeted firmly towards 2011.

"It's not completely solved and we're a bit frustrated we haven't found the solution yet," he reflected of Mercedes' blown diffuser woes. "There are different areas you can use for the floor, and the area that's suffering we didn't anticipate getting as hot as it does. Obviously [with] the exhaust gases moving around the floor, it's sometimes difficult to predict. It's not perfect, but there will be a revision for Monza.

"We've done a lot of work on the car in the last few races, and it hasn't brought the performance we hoped for. Our position has dropped back a bit from where we wanted to be. There's no lack of effort or work or commitment, but we haven't found the performance from some of the modifications we introduced to the level we hoped. We have got to understand that to try and get the full use from them."