Mercedes could face upgrade dilemma for Rosberg

However, the Austrian insists that the manufacturer does not currently have such an upgrade scheduled.

Mercedes introduced an upgraded power unit during the Belgian GP weekend, having used five tokens.

Hamilton has stockpiled three examples of this latest Spa specification, which will take him to the end of the season. Rosberg has only one new example of the Spa spec, but he can take another power unit later in the season, without penalty.

Given that Mercedes still has six tokens to deploy, there is a possibility that Rosberg's fifth engine will be of a spec that features improved performance.

In theory, in the remaining races he would thus have an advantage over Hamilton, who will not want to take a further grid penalty to get the new unit.

"If we find another additional upgrade that's going to be only available to Nico, it's a difficult one, but that's motor racing," Wolff told Motorsport.com.

"One season it goes against you, the other season it goes for you. At this stage we haven't really concluded whether there is enough performance gain in order to upgrade."

Wolff confirmed that if Mercedes does find that performance gain, it will probably be made available to Rosberg: "Then we will probably put it, and that's just how it goes.

"If we find additional performance it's going to help Lewis next year, but we haven't found it yet, so it's an academic discussion."

Hamilton himself accepted that the upgrade scenario could unfold in Rosberg's favour.

"They are constantly developing the engines," said Lewis.

"And there is a possibility that there will be an upgrade later in the year, and I won't be able to take that. But that's the sacrifice I'm forced to take. I've got to take the engines I have, I have no more.

"The engine I finished with at the last race might get through the race, but might not. So we've had to take on these three engines here, which is definitely better than the engine I had in the last race. I'm confident in fighting with those three."

Meanwhile Hamilton will have an extra power unit relative to Rosberg for the remaining races, but Wolff plays down any possible advantage.

"I think first of all you can finish the season with two power units," he said. "So I don't think that gives a real advantage. It just gives you a little bit of a margin in case you run into another problem.

"Lewis was very unfortunate in ending up where he was. And maybe this is a little compensation, but it doesn't compensate for starting last."

Although in theory Hamilton's engines have to run less mileage than Rosberg's in the remaining races, he won't be given an opportunity to run them longer in "turned up" specification.

"We have our specifications on how hard we run the engine, and that counts for every race. There is not an overall allowance of mileage, but an allowance for every race."

However, what Hamilton can now do is use that allocation of "turned up" running to the full, whereas in recent races – mindful of his shortage of engines – he has opted not to do so.

"I can definitely push them more," said Lewis. "There's a certain amount of life which you have, limits which you're given during the race weekend, and I never even get close to them.

"When I had the five engines I was always saving, just saving, saving, hoping to take them further. Tomorrow I'm going to use my allowance, and I can do that in all the races now."