The Belgian club were beaten 4-1 at home by Jurgen Klopp's side a fortnight ago and have yet to win any of the 15 matches they have played in their relatively small Champions League history.
"I brought everyone because I think it is a great moment for the club, for all the players, so my desire was that everyone is here," Mazzu said.
"It is the moment to enjoy but not to be here to take photos. It is to give their life on the pitch and play the best football possible.
"They play a big game against a big team perhaps for once in our life in a place like this.
"I know the results are not so good and the way we have played is not so good. I know it's not an easy moment but I am calm. I don't feel the pressure.
"We play against the best team in the world at the moment. I am sure the players' mentality will be better tomorrow - and I hope the coach's also."