Valtteri Bottas and Lewis Hamilton will be team-mates at Mercedes in 2017
Valtteri Bottas signed a one-year deal with Mercedes last month to replace Nico Rosberg.
The German retired as world champion just five days after sealing the title with team-mate Lewis Hamilton forced to settle for second place.
But Alex Zanardi, who raced 41 times in F1 but is perhaps better known for his four Paralympic gold medals after losing both legs in an IndyCar accident, believes Bottas cannot challenge the Brit in the same way that Rosberg did.
F1 2017 driver line-up
Mon, February 13, 2017
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Mercedes – Lewis Hamilton (44)
"Hamilton has proved several times that he has an extra level compared to the others," Zanardi told Italian newspaper La Gazzetta dello Sport.
"Rosberg managed to beat him, but that was about his extra qualities.
“Bottas is a very good driver, no question, but he's not a Nico."
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Lewis Hamilton could drive to a fourth world title in 2017 – his third with Mercedes
Alex Zanardi had a successful racing career before and after losing both legs in an accident
The coming season will see a new set of rules and regulations debuted in an effort to encourage overtaking and increase cornering speed.
But the changes are not expected to break Mercedes’ iron grip on the Constructors’ Championship, which they have won for the last three years.
However, Zanardi expects Red Bull, traditionally fastest at adapting to such alterations, to mount the main challenge.
"For Lewis, [having Bottas as a team-mate] makes it all the easier for him to dominate the championship,” Zanardi added.
“Behind him I see better chances for Red Bull to chase Mercedes than Ferrari.
“I trust Daniel Ricciardo, and most of all Max Verstappen, a lot.”