Four-time world champion Alain Prost reckons Nico Rosberg's answered a lot of his critics with the manner of his Singapore Grand Prix victory as he "had to fight for it".

Rosberg claimed a third straight win, and eighth of the season, at Yas Marina, holding off a late surge from Daniel Ricciardo to win by 0.4s. The win moved him ahead of Lewis Hamilton and into the lead of the championship by eight points with six races to go.

Though some have questioned the nature of Rosberg's other wins this season, Prost thinks the German's drive in Singapore proved he can win when he's under pressure.

"Nico delivered a fantastic weekend in Singapore with an incredible pole position on Saturday followed by a very mature drive on Sunday," Prost told French broadcaster Canal. "You could feel him very much in control all weekend, whereas Lewis Hamilton was not. He did not really perform and looked a bit shaky.

"Rosberg took a commanding win but still had to fight for it, something that had been awaited of him for a while."

Momentum has swung dramatically between the Mercedes drivers this season -- Rosberg's victory in Baku is the only time either he or Hamilton have not won two or more races in a row. Prost believes the pair are so close in terms of performance the title will be decided on "small details".

"You can see the momentum shifting often at Mercedes. When one driver if performing, the other looks a bit off. We have yet to see them compete wheel-to-wheel but I think it will happen before the end of the season.

"The title will be decided on small details, like the starts, another car splitting the Mercedes - one place can make a big difference in the end -, but it will also be a mental fight.

"Before Singapore, you'd have thought Hamilton had the upper hand in that area but Rosberg has showed us he can be really solid as well."