N’Golo Kante has endured a difficult campaign this year.
The French midfielder has been compared with modern-day greats such as Neymar and Mbappe.
Kante had various muscular problems and a groin injury that stalled his chances in the first-team this season.
He has one-year left on his Chelsea contract and the club soon needs to find a solution to his injury problems.
Tuchel said: “I think he is our key, key, key player but key, key, key players need to be on the pitch and if he plays only 40% of the games, it is maybe a miracle that we arrive in third place. He is our Mo Salah, our [Virgil] van Dijk, our [Kevin] De Bruyne.
“He is simply that player. He is our Neymar, our Kylian Mbappe, he is the guy who makes the difference and if you only have him 40%, it is a huge problem.
“It is maybe a miracle of how consistent we produce results and puts everything into perspective because I saw Liverpool last season without Van Dijk and they struggled heavily. You see the difference. N’Golo is our key player but he needs to be on the pitch.”