Zenit St Petersburg need a miracle at Borussia Dortmund in order to reach the Champions League quarter-finals, according to their caretaker coach.
The Russian side suffered a 4-2 home loss in the first leg of the last-16 tie and subsequently sacked Italian coach Luciano Spalletti.
He has been replaced by ex-Tottenham boss Andre Villas-Boas, although Sergei Semak will be in charge on Wednesday.
"Our chances are slim, but miracles sometimes happen," Semak said.
Zenit are at least near full-strength for the game, while Dortmund will be without winger Marco Reus, with fellow Germany midfielder Sven Bender not expected to be back until late April because of a groin injury.
Dortmund have won eight of their last nine Champions League home matches. Their only defeat came against Arsenal during the group stage in November.
Reus, 24, was on target in the first leg win in Russia last month, but has not played in the last two league games, including the 2-1 defeat to Borussia Moenchengladbach on Saturday.
"Unfortunately he could not participate in team training today and will not be available for us tomorrow," Dortmund coach Jurgen Klopp said.
Klopp, who has had to reshuffle his team throughout the campaign due to a long injury list, said their first leg win had given them a slight edge but Wednesday's game was far from settled.
He added: "The plan is to make a normal football game out of it. We ideally go into this game as a second half of a match. The first leg was nothing more than the basis for the second leg.
"In the first leg, we put ourselves in a good position for the return leg. Nothing more, nothing less. We will not risk a lot, but just going out there to defend our lead would be a bit stupid as well."
The German coach, sent off again in the Bundesliga during the weekend for arguing with a fourth official, also took some pressure off his players, saying the club's goal had already been achieved when the team made it past the group stage.
"We have reached our goals by making the knockout stage. Anything beyond that is bonus for us but we still want to get the maximum out of this competition," said Klopp, who steered Dortmund to the final last season.
"But there would not be a big hole in our budget should we go out."
Despite being odds-on favourites to progress, full-back Marcel Schmelzer insists last year's runners-up are taking nothing for granted.
"We don't believe that we are already in the quarter-finals," he said. "St Petersburg will demand a lot of us all."
