The Blues progress to the quarter-finals with Tammy Abraham's second-half goal but the German coach felt his team should have played better.
Tuchel said: "We scored the goal and I had the feeling that they increased the risk, but we stepped down in the little decisions.
"Not enough courage and it was too deep for a long, long time. We clearly can play better, so yes I expected more but not in terms that I am frustrated."
"We can do better but I don't want to be too hard on the players."
Tuchel admits that a tactical switch at half-time helped his players gain more control of the game.
He told BBC Sport: "We changed to a back four and took Marcos [Alonso] out for this tactical change. Andreas [Christensen] had to go out because he had a headache. The changes made it a little easier to get into the opponent's half and overcome the first press.
"We did it well at the start of the second half and played constantly in the opponent's half."
Tuchel added that he was pleased to see his team come through a potentially tricky game against their second-tier opponents.
He said: "If you lack a rhythm and a bit of self-confidence and you have to show on this pitch, against an opponent that takes all the risk and plays the game of his life, that is not easy."