The Blues were fortunate to claim a 1-0 victory at Oakwell, which booked a meeting with Sheffield United in the FA Cup quarter-finals.
"We changed to a back four and took Marcos [Alonso] out for this tactical change," Tuchel said after the game. "Andreas [Christensen] had to go out because he had a headache. The changes made it a little easier to get into the opponents half and overcome the first press.
"We did it well at the start of the second half and played constantly in the opponents half.
"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.
"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. We can do better but I don't want to be too hard on the players."