Tuchel has deployed a 3-4-3 formation since taking over from Frank Lampard in January and Mateo Kovacic and Jorginho have been a mainstay of the team.
“Since I arrived, the only thing that kept him from making a big impact is his injury, nothing else,” the Blues boss said.
“I see a committed guy, I see a guy who made a brave decision to move abroad at a young age and to go out of his comfort zone and accept a big challenge in a big team, in the biggest League.
“I see a totally clear guy who is totally aware of that, full of talent, unlimited talent and I see a player who will have a big impact in Chelsea, I’m absolutely convinced.
“The mix gives me that feeling that he can have a big role in this club and he is absolutely determined to fulfil his role.
Havertz joined Chelsea in the summer in a big-money move from Bayer Leverkusen, but he has been unable to find his feet at Stamford Bridge.
He has only scored one Premier League goal for Chelsea.