Semak is set to take caretaker charge for the final time on Wednesday, with former Porto, Chelsea and Tottenham boss Villas-Boas having been officially announced as Luciano Spalletti's replacement on Tuesday.
But the 38-year-old feels Zenit may have too much of a mountain to climb against Dortmund after losing the home leg of their UEFA Champions League last 16 tie 4-2.
"Everything is possible in football. Of course, we do not have a lot of chance," he said. "Tomorrow we are up against one of the best sides in Europe, even in the world. It will be important for us to put in a good performance.
"BVB (Dortmund) have a very strong side. They are very strong when it comes to attack.
"For us, it is a new experience to play here and we will surely learn a lot new things. It is not easy playing against such a team.
"We have not had a lot of time to change things. It was the most important task for me to bring the team together, to instil a team spirit. We have many individually great players, but I wanted to improve their team spirit, their sense of togetherness.
"We have real professionals, I want to improve their team spirit and want them to present themselves from their best side.
"The situation is not easy for me. The result is only interesting to me if it is good enough for a win.
"It is important for us to present our best, to stick together and not be sorry for anything afterwards. Only then will we have a chance to turn this around."
