Tsunoda showed flashes of speed and promise in 2021 but his rookie season was also marred by various crashes and errors as the Japanese youngster was overshadowed by teammate Pierre Gasly.
Tsunoda raised eyebrows with a ninth place on his Bahrain debut but then struggled to build on that result.
While Gasly consistently raked in the points to keep AlphaTauri in the fight for fifth in the constructors' championship, Tsunoda's confidence took a knock as he claimed only six further top-10 finishes.
It took a mid-season move closer to AlphaTauri's Faenza base in Italy and a more disciplined approach for Tsunoda - who called himself a "lazy bastard" - to dig himself out of his early season hole.
Team principal Tost said he never questioned that the highly rated Japanese youngster could turn it around. But ahead of the 21-year-old's sophomore year, Tost says "it is now in his hands" to turn his raw talent into results.
"I can only say that Yuki is a really fantastic driver," Tost said. "Now, it's also in his hands what he is making out of this, because to have talent is one story. I know a couple of F1 drivers that were really talented, but they won maybe one race or even no race.
"As a Formula 1 driver you cannot do enough physical training, nutrition is very important, to be really disciplined. And the complete way of life must be 100% matching what Formula 1 requests.
"This is now in his hands. We can only advise him, but then he has to do it by himself. And this is where you will see [if he] can become a real top star. From the driving side he can do it. Now it's up to him."
Tost said Tsunoda's year was "a fantastic example" of a rookie season, which looked worse than it was because he was paired with an outstanding and now highly experienced Gasly.
"Yuki's season is a fantastic example of a rookie season." Tost explained. "It was in the past always the same, but this year was the first time that there was a very experienced driver on the side of a rookie.
"Normally we started with two rookies or a driver with one year of experience and then the difference was not so obvious.
"What happened with Yuki is totally easy to explain. [In Bahrain] he did a good race, finished ninth, everything fantastic. And it was clear for me a crash would come soon, because Yuki drove already on the limit.
"But it's always the same with young drivers. We tell them 'hey, you are on the limit' and I know exactly what Yuki had in his head. After Bahrain he thought – and that's typical for young drivers – 'huh, Formula 1 is not so difficult'."
Those crashes duly came, with an aggressive Tsunoda crashing out in Imola in both qualifying and the race, followed by further offs in subsequent races as his confidence started taking a knock and a move to Italy was arranged.
"He was shocked, he lost confidence," added Tost. "Of course, then the question comes: "Am I able to do this? Maybe Formula 1 is too fast for me?' It's with all the drivers the same. but with Yuki it's just such a fantastic example.
"This is the reason why I say a young driver needs minimum three years to understand a little bit Formula 1, because Formula 1 is much more complex as people think.
"Next year is a completely different story because he knows much more. I'm quite confident that we made the right decision."
