"I knew I was one of the candidates, one of the possible drivers," said Wehrlein in an interview with Motorsport.com this week. "But one year of experience is not enough, it was quite clear.
Wehrlein said that the situation had been explained to him personally by the head of the Mercedes F1 team Toto Wolff.
“That is what he said," Wehrlein recalled. "He said, ‘We think it would be good for you to have more experience. One year was not enough. Especially in the second year, drivers are always making big progress.'
"I think Mercedes wants to have a ready driver and a perfect driver, who is at his limit.
"At the moment I am not on my limit where I could be, because of the experience, and that is quite clear."
The 22-year-old won the 2015 DTM championship with Mercedes before switching to Formula One. He spent a year with Manor, and this season will race for Sauber.
Even though he can see the logic of Wolff's decision, Wehrlein said that he certainly wouldn't have turned down the opportunity if he'd been asked.
“If the chance is there, you have to take it,” he said. “I think it was not too much. Of course with one year of experience you are not at your limit and you will do some mistakes.
"If you have five years of experience in F1 or even more, you know, the mistakes – they will be a lot less than with one year," he added.