Toro Rosso boss Franz Tost believes that Pascal Wehrlein isn't ready for a promotion to 2016 Champions Mercedes just yet.
Tost has seen plenty of his drivers earn promotions to Red Bull racings primary team and knows a thing or two about what is required to make the step up to a big team.
Mercedes face a choice between Wehrlein and William's driver Valteri Bottas to replace world champion Nico Rosberg who shocked the world when he announced his retirement at the end of the 2016 campaign.
Tost doesn't feel that Wehrlein is the right fit to replace compatriot Rosberg at Mercedes.
"They (Mercedes) were in a very difficult situation," Toro Rosso team boss Franz Tost said in an interview with German newspaper Tiroler Tageszeitung. "They have dominated but suddenly lost the world champion, and it happened too late for them to replace him with a top driver because of all the contracts."
"Pascal is a great backup driver, but we are talking about the champion team," he said. "Pascal may be able to fight for victory, but it's too early for him. I've always said that it takes three years for a driver to get comfortable in Formula One."
"Of course, Hamilton-Wehrlein was the easiest option for them, but they are fighting for the constructors' championship and a lot of money is at stake.
"And it's also not clear if that driver composition would have a bad influence on the stability of the team," Tost added.
According to f1today.net Mercedes' number one elect Lewis Hamilton vetoed the idea of Wehrlein driving for the team.
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