Jakub Blaszczykowski made the tie safe late on as Dortmund secured a place in the competition's quarter-finals for the first time since 1998.
SHAKHTAR: Pyatov, Kucher, Raţ, Rakitskiy, Hubschman, Fernandinho, Teixeira, Srna, Adriano, Mkhitaryan, Taison
"It is a very, very important match for us because this side have the opportunity of reaching something new, the quarter-finals of the Champions League.
"It will be difficult for either team, the first leg decided nothing. Our position is maybe a bit better, but no more than that. I'm not worried about us making mistakes. There is no such thing as a football match without mistakes. It's about performing so well that your mistakes don't matter in the larger scheme of things. It's now about how well the lads on the pitch perform, that's what's decisive."
He told reporters: "I think we are well prepared although Dortmund are a very strong side. They advanced from a group containing Ajax, Real Madrid and Manchester City and created six or seven clear chances against all of them at home.
"Despite being well-oiled in the Bundesliga, they profited only from our mistakes in the first leg. For [Robert] Lewandowski's goal, two of our players got in each other's way and it was similar for their second goal. Dortmund might be in better shape, physically. They are playing at a very high level, be it with vertical or horizontal passes, low or high balls. My team will aim to make fewer mistakes and avoid handing them any presents.
"Dortmund will make life difficult for us and go on the attack from the off, backed by those fans. We will come under pressure at the back. The team which goes through tomorrow will surely reach the Champions League final. Klopp is a great coach, world class."