Two second-half strikes powered Tricolor dos Pampas to a 2-1 triumph in the first leg of that tie in Porto Alegre last Tuesday.
Match preview
After a late defensive collapse, the defending champions are on the ropes and need a victory to maintain any hope of retaining their title.
It was their first defeat of the tournament this year, and the first time they came away empty-handed from a Libertadores knockout fixture since 2013 (2-1 versus Olimpia).
Heading into this must-win affair, Fluzao are in a bit of a slump, winless in four successive matches across all competitions, playing to a 0-0 draw with Corinthians domestically on Saturday.
In the opening round, Mano Menezes' men won all three of their home matches by a single goal, and they are undefeated in their last four competitive fixtures at the Maracana.
This is the first time since 2013 that they lost the opening leg of a Libertadores knockout fixture when Emelec beat them 2-1, but Flu advanced thanks to a 2-0 victory in the decisive game played in Rio.
Fluminense have never lost to a Brazilian opponent at home in the knockout portion of this tournament, with their last such triumph occurring in the 2012 round of 16 versus Internacional (2-1).
A resilient showing by Gremio last week has them on the brink of making the quarter-finals of this competition for the first time since 2020.
Renato Gaucho's men scored twice in three minutes to erase a 1-0 deficit and extend their unbeaten run in this tournament to five matches.
Throughout this competition, Gremio have not been intimidated when entering enemy territory, winning their last two away matches by a 1-0 margin.
They head into this encounter on a four-game unbeaten run away from home across all competitions, claiming a 3-1 domestic win over Cuiaba earlier this month.
Not since 2018 has this club been eliminated from a Libertadores knockout tie when winning the opening leg, losing 2-1 to River Plate and exiting the competition on away goals.
Imortal Tricolor are unbeaten in three previous meetings with Fluminense at this tournament, winning their only prior visit to the Maracana in this competition, 3-0 in 2013.
Fluminense Copa Libertadores form:
W
D
W
W
W
L
Fluminense form (all competitions):
L
W
D
L
L
D
Gremio Copa Libertadores form:
L
W
W
W
D
W
Gremio form (all competitions):
D
W
L
W
W
L
Team News
For this decisive contest, Fluzao could be without German Cano, who has a sore foot, while Marquinhos and Marcelo may not be available due to thigh injuries.
Diogo Barbosa is not expected to return until early November from a meniscus issue, and Matheus Martinelli could be out once again because of an ankle injury.
Lima put home the opening goal for Fluminense last week, the first for the ex-Gremio midfielder at the Libertadores this year.
A straight red card in the 84th minute means that defender Rodrigo Ely will have to sit out of this fixture for Gremio on Tuesday.
Jhonata Robert missed the previous match of this tie with a sore knee, Andre has an ankle issue and Mayk is recovering from a muscle injury.
Reinaldo came through with two goals in the final 16 minutes to put his side in the driver's seat heading into this encounter.
Fluminense possible starting lineup:
Fabio; Xavier, Silva, Santos, Esquerdinha; Andre, Matinelli; Arias, Ganso, Keno; Kennedy
Gremio possible starting lineup:
Marchesin; Pedro, Martins, Jemerson, Reinaldo; Villasanti, Dodi; Pavon, Cristaldo, Soteldo; Braithwaite
We say: Fluminense 1-0 Gremio (Gremio advances on penalties)
Gremio have won eight successive competitive games against Fluminense by a single goal, and we believe that will give them a psychological edge on Tuesday.