Benfica will need to end a four-game winless run to reach the quarterfinals of the Champions League at the expense of Zenit St. Petersburg.
The Portuguese club is aiming to overturn a 3-2 deficit in the second leg of the round-of-16 series on Tuesday.
Benfica will have to do that without key Argentine pair Ezequiel Garay, a central defender who is out with a left knee sprain, and suspended playmaker Pablo Aimar.
Benfica surrendered its Portuguese league lead at the weekend, losing at home to FC Porto for its third defeat in four matches to drop to second place.
The slump, which began in St. Petersburg, is Benfica's worst run of results in three years and has raised Zenit's hopes of going deeper into the competition than ever before.
The Russian champions are six points clear at the top of its domestic league and drew 2-2 at CSKA Moscow on Saturday, with striker Alexander Kerzhakov scoring both of Zenit's goals.
''The game against CSKA was the most important one during my work at the club, but the match against Benfica will be the most important one in the club's history,'' Zenit coach Luciano Spalletti said.
Zenit was without seven key players in the first leg, its first game of the year, but can count on the return of goalkeeper Vyacheslav Malafeev, defender Domenico Criscito and strikers Danko Lazovic and Alexander Bukharov.
''We have a perfect chance to make it into the quarterfinals,'' midfielder Sergei Semak said.
Benfica was unbeaten in the Champions League this season before its trip to Russia. It reached the knockout round after finishing top of Group C, which included Manchester United.
Paraguayan striker Oscar Cardozo scored twice in Benfica's 3-2 loss to Porto and is the joint top Portuguese league scorer with 16 goals in 21 games. But Benfica's midfield has recently lost its sparkle.