Rangers were left reeling when Dan Petrescu's men left Glasgow with a 4-1 victory and Varga knows tonight's clash will have a huge bearing on the fortunes of both teams in the competition.
He said: "We all know this is a life or death match - especially for Rangers as this is their last chance to qualify from the group stages.
"So we know they will play the game of their life. It will be a more difficult game than the one in Glasgow because they will come here for their morale and for their pride and that's why we believe it will be more difficult."
The game will be played in the Steaua Stadium in Bucharest, around 25 kilometres from the town of Urziceni, which holds a population of just 17,000, and Varga urged their fans to make the journey and throw their backing behind the team.
He said: "It's very important to play with a full house because it would give us more power and I assure the people who come to the stadium that they won't be disappointed."
Petrescu added: "Some games we have three or four thousand people so maybe there will be a couple of thousand from our city here and hopefully, like Stuttgart, another 15,000 from Bucharest.
"Someone told me that maybe the stadium will be full and that would be fantastic because we need the supporters as Rangers will have a couple of thousands fans and they know how to help the team."