Bottas was signed by Mercedes last month as replacement for retiring world champion Nico Rosberg, but his deal is only fixed for one year with options to extend it beyond that.

Mercedes has been clear that the reason is that it wants to wait and see how Bottas performs before committing any longer - as well as leaving the door open on drivers like Sebastian Vettel and Fernando Alonso who could be available for 2018.

Speaking about the situation for Bottas, Salo told Motorsport.com: "It's just surprising, to make a one-year contract in Formula 1 nowadays.

"Everybody wants to make long-term contracts. I just don't know what the reason is behind it."

In response to Toto Wolff's explanation that keeping options open was essential, Salo added: "I guess that's the only reason I can imagine, because Valtteri is good enough to sign for longer term. So, we'll see. I guess they just want to see how he performs and then see after that.

"They put Valtteri in a very difficult situation, against Lewis [Hamilton], on a one-year contract. It's not easy."

However, Salo believes Bottas is strong enough to overcome the added pressure of not having a deal past 2017.

"It will be plenty [of time]. It's no problem," added the ex-Tyrrell, Arrows, Ferrari and Sauber driver. "He's a professional guy, he has four years in Formula 1 already, so it's not a big deal.

"It's just that when you have peace of mind that you will continue, you can perform better."

Hamilton match-up

Salo reckoned that, should Mercedes remain the benchmark of the field, it would be a reasonable target for Bottas to follow Hamilton close – and even beat him "sometimes".

"[It] depends on the Mercedes quite a lot, what kind of car they can make. Let's see how good the car is," said Salo.

"I would imagine that it's still the best, but then what Valtteri has to do is finish second behind Lewis all the time and even beat him sometimes."

Asked whether Bottas should aim higher than only occasionally beating Hamilton, Salo explained: "I rate Lewis very highly, he's very good in qualifying.

"I'd like to think that Valtteri is maybe even a little bit better in the race. He's kind to the car, kind to the tyres, so he might have a good chance in the races."