The hosts ended last season runners-up in the top flight, while their opponents have collapsed domestically despite claiming the 2023 Copa Libertadores.
Match preview
Gremio were meant to build on last season's title challenge by pushing for a third title and a first since 1996, but they have utterly failed to meet those lofty heights.
While they undoubtedly overachieved last season in their first year back after relegation in the 2022 season, few would have foreseen the magnitude of their floundering 2024 season.
The club's glaring drop-off is underscored by their current ranking — second-bottom — after 12 gameweeks, even if they have so far played 10 matches.
Regardless, the club have kept faith in their icon Renato Gaucho despite increasing pressure on the 61-year-old to deliver results for last term's second-placed side.
Imortal Tricolor ended a four-match losing run with a point against fellow strugglers Atletico Goianiense in midweek, with Reinaldo scoring an 82nd-minute equaliser to prevent a fifth consecutive Brasiliero defeat.
However, Gremio need wins very quickly to avoid the ignominy of dropping out of the top division having ended last season so close to the title.
Fluminense hope to prevent the hosts' first league success since a 1-0 win over Cuiaba in late April that followed a 2-0 win over Athletico Paranaense. However, they must end an even poorer run of one win in 12 league matches.
While last year's Libertadores winners ended seventh in the top division last term, this season's breakdown has caught many observers by surprise.
The upshot of their pitiful start has been Fernando Diniz's recent dismissal with Marcao in caretaker charge of the club at the time of writing.
The interim boss thought Flu were ending a four-match losing run against Vitoria in midweek, only for a Janderson goal to settle proceedings in the first minute of second-half stoppage time, with the 1-0 home loss inflicting the cellar-dwelling club's eighth loss this season — a joint low with Vasco da Gama.
Worrisome for Fluminense during their ongoing run of losses has been the absence of a goalscoring threat, with the away side scoring once in the loss against relegation-threatened Atletico Goianiense (2-1) while failing to score in defeats by Botafogo (1-0), Cruzeiro (2-0), Flamengo (1-0) and Vitoria (1-0).
This magnifies where the issues are for Flu heading into this weekend's match as they aim to stop the rot against their relegation rivals.
Gremio Brasileiro form:
L
L
L
L
L
D
Gremio form (all competitions):
D
L
L
L
L
D
Fluminense Brasileiro form:
D
L
L
L
L
L
Team News
Yeferson Soteldo (Venezuela) and Mathias Villasanti (Paraguay) are on Copa America duty and unavailable for Gremio's match against Fluminense.
Erstwhile Atletico Madrid and Chelsea centre-forward Diego Costa has a muscle issue, while Andre Henrique (ankle), Lucas Mila and Jhonata Robert (both knee) are not expected to play for the hosts.
Despite the home side's struggles, only Flamengo's Pedro (four) has scored more match-winning goals than Franco Cristaldo (two) in the Brasileiro, and the advanced midfielder aims to have a telling impact on Sunday.
Thiago Silva's return to Fluminense does not become official until July 1, meaning the visitors must do without the experienced centre-back for one more match at least.
Jhon Arias is with the Colombia squad at the Copa America finals in the United States and is unavailable for selection, but Lima returns from suspension for the visitors.
Missing due to injury worries are Vinicius Lima (muscle), Marquinhos (thigh) and Andre Trindade (knee).
Gremio possible starting lineup:
Marchesin; Pedro, Martins, Kannemann, Reinaldo; Dodi, Pepe, Cristaldo; Galdino, Galvao, Pavon
Fluminense possible starting lineup:
Fabio; Xavier, Carlos, Santos, Marcelo; Alexsander, Lima; Terans, Ganso, Keno; Cano