The Formula One drivers Lewis Hamilton and team mate Jenson Button are divided as to how a wet practice session will affect McLaren's German Grand Prix prospects.
In a rare case of disunity between the two champions whose pairing has been notably harmonious, Hamilton says forecast rain on Friday would be a setback for the team in what has been billed as a key test of new aerodynamic components.
However Button, the reigning Formula One titleholder, felt it would make no difference.
McLaren tried to introduce a new blown diffuser, a system channelling the hot exhaust gases down and out through the rear of the car to create more grip, at the previous British Grand Prix but had to ditch it when it proved problematic in practice.
The team, top of the standings despite Red Bull having taken nine out of 10 pole positions, intend to try out a modified version this week before deciding whether to use it in Monday morning's race.