The Blues won the second leg of their Champions League semi final 2-0, and went through to the final thanks to a 3-1 aggregate success.
Havertz, who played a key role in the first goal of the game, was in fine form in the previous game against Fulham in the Premier League as well.
"For him in a good way [Havertz gave the manager a positive problem]," Tuchel told BT Sport before the game.
"Christian got a bad message for him today unfortunately, but I'm pretty sure we need more than 11 players to sneak through today.
"It's good to have Christian from the bench. Kai gives us a little bit of height also against the set-pieces and maybe in fast attacks can keep the ball."