Last Wednesday in Germany, three explosions went off as the team headed to the stadium for the home leg against Monaco, leaving defender Marc Bartra needing hospital treatment following injuries to his wrist and arm after a window was shattered.
The match was rescheduled for Thursday and Monaco won 3-2 to put themselves in a strong position to reach the semi-finals.
At that point, Tuchel's mind was far away from football and he was angry that UEFA had not taken the attack seriously enough as it swiftly rescheduled the game. The club's chief executive Hans-Joachim Watzke even considered withdrawing the club from the competition.
On the eve of the return leg, the mindset of Tuchel and his players is different: a mixture of pride, motivation and defiance.
"We've got this out of our system now, and we're more stable emotionally," said Tuchel, who was speaking through a translator at the pre-match news conference.
"All that happened last week has made us stronger. Now we have to play well and I'm convinced we can do that. We're ready and focused. We know it will be very tough, but we have the energy and confidence we need to get a result."
Tuchel has become more than a manager to his players in the last few days, reaching out to them on an emotional level.
"It's a situation that we're all discovering together. We have to find a way to get through everything that happened together," Tuchel said. "We're the only ones who can understand what happened since we were there.
"I'm a part of this helpful process, and it's a joy to see how much the players talk to each other and respect each other's emotions," Tuchel said. "I try to help by sharing my feelings and we learn things together through this process."
Some of the more experienced players, like 27-year-old attacking midfielder Marco Reus, have also been helping him.
"The players have different ways of getting rid of the stress. My goal is to aim the younger players in the team, help them if they want to talk about it and if I can offer them some support," said Reus, who scored last weekend in a 3-1 home win against Eintracht Frankfurt. "We've become much closer in the last few days."
Reus says football, in this case, has a therapeutic quality.
"It's not a question of fear; it's actually good for us. We're thinking about something else, we're not all stuck at home," he said. "Such an event can give you more energy and brings you closer together."
On the pitch, Monaco must find a way to score at least twice against a Monaco side that boasts a fearsome attack.
"We've faced a lot of teams who have very good strikers and we know what to do," Reus said confidently. "We believe in our ability and we know we can score goals."
Not conceding them, however, is somewhat difficult against a Monaco side that has scored 138 goals this season, and boasts one of the hottest young talents in football.
Teenage attacker Kylian Mbappe has scored 21 goals, including two in the first leg last week. The newly-capped France international forms an electric attack alongside rejuvenated Colombia striker Radamel Falcao, who has 26 goals this season.
"We have an advantage and we're aware of that, but Dortmund is a great side," Falcao said. "It's clearly a mistake to think that we're through. Our mentality shouldn't change."
Coach Leonardo Jardim expects a harder contest.
"I think that Dortmund is stronger psychologically now. I'm expecting to face a stronger team that has come through (what happened)," he said, adding that Monaco will not sit back and defend its lead.
"My team is used to playing a certain way and that will not change. We might need to score tomorrow."