Wolff understands lack of F1 2018 contract puts pressure on Bottas

Bottas was signed as a last-minute replacement for 2016 world champion Nico Rosberg over the winter, initially on a one-year deal to partner Lewis Hamilton.

Speaking at the FIA Sport Conference in Geneva, Wolff said he was pleased with Bottas's start to life at Mercedes, but he stressed the Finn knew he would be unlikely to secure a contract extension early in the campaign due to the number of top line drivers - including Sebastian Vettel and Fernando Alonso - who are out of contract at the end of the season.

"Of course it's an uncomfortable situation for him with quite some pressure," said Wolff.

"When we decided to make Valtteri the offer, he knew that we would be taking our time with the decision going forward because the driver market is more open in 2018 and beyond - 2018 and 2019.

"That's why we will not rush into a decision, but continue to work with him and see how that pans out.

"But generally the view of the team is that he's done a good job.

"The call he received was pretty late, he's driving against one of the best drivers of Formula 1 that has been with the team in his fifth season and he's had a pole position, won a race in Sochi in a very dominant way and he's had the more difficult races.

"But overall his performance on-track and the way he has integrated with the team was very positive."

BOTTAS HAS PROVED HIMSELF

While Wolff accepts that Bottas's move to Mercedes on a short-term deal was a risk, he believes the 27-year-old has boosted his reputation by proving himself in a top car.

"He has taken a decision to leave Williams and join Mercedes in a one-year deal," he said.

"I think that the perception of him as a racing driver has gained.

"He's won a race rather than lost, so I think it already paid out."

Wolff also added that the fact Bottas brought sponsorship money with him to Mercedes this year increased his appeal, even if it wasn't the key factor behind the team choosing him as Rosberg's replacement.

"Today the revenue model for some of the teams, for most of the teams, is also actually to generate income," he said.

"Even if we look at a Red Bull or a Mercedes I would rather have a driver with some sponsorship than not.

"Even Valtteri for example, part of his value proposition for this year was that he came with a sponsor and clearly we would rather have the money than not."