"We don't approach games like this, to talk about the result we have and then change the approach to our game," Tuchel explained of the aggregate advantage. "It's important that we are fully focused on us playing the best game possible again because this increases all the chances to have a result.
"In terms of adapting to the result, it's easier for Porto because they know very well what they need to do. They need to score three goals if they want to go through so for them it's absolutely clear.
"For us, if we think like this then we could absolutely lose our heads because what does it mean? That it's enough to lose 1-0 or it's good to draw? Why should we enter into this thinking?"
Tuchel also warned: "You have to accept against Porto that it's a little bit up and down in some minutes and we experienced that in the first leg.
"We managed to control the match in some minutes, to create half-chances, to find some space for acceleration and to have good counter-pressing. But in some minutes they escaped the pressure and they can be very dangerous with runs and dribbles and individual quality. They overload the sides and they are very strong on set-pieces so they give you a lot of questions to answer.
"They can shift the momentum but it's a totally normal thing because it happened in all their matches against Manchester City and Juventus [earlier in the competition]. They have quality, they are a proud club and a very emotional team so this is what we have to accept.
"We should not over-expect from ourselves or lose our temper and patience because of these moments where it's getting difficult. If it happens again, don't worry because it's normal."