Nico Rosberg takes fourth engine of F1 2015 for Singapore GP

Rosberg and team-mate Lewis Hamilton both moved onto a third power unit for the last race in Italy when Mercedes used its final seven development tokens as it explored a new development direction.

But the German was forced to switch back to the previous-spec engine ahead of qualifying due to a problem, later discovered to be a leak in the cooling system that ultimately had a knock-on effect to the power unit.

With the system sealed in between events, Mercedes has only been able to carry out an inspection of the unit that will be fired up again on Thursday.

Mercedes will then be able to determine the engine's health and whether it is fit to at least be put through its paces in practice.

Whatever the situation, the team has confirmed Rosberg will take on a fourth power unit for the race, which will be the updated version that was introduced at Monza.

With seven races remaining Rosberg will then stand on the brink of a 10-place grid penalty should he be forced to take a fifth unit at any stage.

That would be a further blow to his championship chances, with the German already 53 points behind Hamilton with 175 up for grabs.