While the Rio giants seek a lead to take to Curitiba for next week's return, Athletico are intent on ending their defence of Brazil's national knockout competition.
Match preview
Nearly twelve months after eliminating Athletico Paranaense in the 2022 Copa do Brasil quarter-finals, en route to lifting the trophy with a penalty shootout win over Corinthians in the final, Flamengo find themselves back in the same situation.
The four-time winners edged out their counterparts from Parana 1-0 on aggregate last year, and after coming through this season's last-16 stage via a 2-0 victory against Rio rivals Fluminense, the pair now meet again.
Leading Athletico by five points in the Campeonato Brasileiro standings, where they sit third after 13 rounds, Flamengo welcomed Fortaleza to the Maracana last weekend, and a 2-0 win was their fourth success from five in all competitions.
During that time, Jorge Sampaoli's side have also serenely progressed from the Copa Libertadores group stage, with an impressive attack helping them push for glory on all three fronts.
Indeed, no other team in Brazil's top flight have netted as many goals as the Rubo-Negro's 26 so far, and exploiting such firepower will form much of Sampaoli's plan on Wednesday.
Though they sit six places lower in the Serie A standings, Athletico Paranaense went one better than Flamengo in the Copa Libertadores last week, when they secured top spot in their group with a comprehensive 3-0 win over Allianza Lima.
Then, at the weekend, they went on to salvage a point in the Brasileiro after trailing by two goals midway through the second half; extending their unbeaten streak to three games.
Once again, teenage star Vitor Roque was on hand to help his team out of trouble, and after scoring three goals in his previous three league appearances, the 18-year-old netted in the 72nd minute to secure a 2-2 draw with Palmeiras - incidentally, Real Madrid-bound Endrick, aged just 16, had opened the scoring at Arena da Baixada.
Athletico boss Wesley Carvalho, who took charge as interim coach following Paulo Turra's exit in mid-June, seems to be turning things around slowly but surely, and with Vitor Roque yet to be spirited away to Europe for mega-money, targeting the club's second Copa do Brasil crown remains a realistic ambition.
As Carvalho's arrival has heralded a more progressive approach, the visitors may even go toe-to-toe with favourites Flamengo in Wednesday's first leg - one of seven July fixtures for Athletico, who visit fellow mid-table side Fortaleza in the Brasileiro this weekend.
Flamengo Copa do Brasil form:
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Flamengo form (all competitions):
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Athletico Paranaense Copa do Brasil form:
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Athletico Paranaense form (all competitions):
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Team News
Aiming to keep a large squad happy while maintaining momentum in all competitions, Jorge Sampaoli is expected to make several changes to his starting XI in midweek - particularly as Palmeiras await in the Brasileiro on Saturday.
Therefore, a reshuffle in defence could see David Luiz return to the heart of the hosts' back four, while Victor Hugo may start in midfield.
Brazil striker Pedro is another contender to be promoted from the bench, but Giorgian de Arrascaeta - who won the 2022 Copa do Brasil's best player award - and Gabriel Barbosa, who scored his 150th goal for the club last weekend, are the men in possession up front.
After saving a penalty in the first half of Fla's win over Fortaleza, 22-year-old goalkeeper Matheus Cunha will hope to keep his place; only Matheuzinho, Matheus Franca and veteran midfielder Arturo Vidal are unavailable due to injury.
Athletico made an enforced switch in the goalkeeping department last weekend, as Leo Linck made his Brasileiro debut in the draw with Palmeiras - saving an Endrick penalty and pulling off a series of smart stops throughout.
However, Bento is now back from suspension and should start at the Maracana, behind the back three which has been Wesley Carvalho's preferred choice over the past fortnight.
The visitors have most of their squad to choose from, with just injured trio Fernando, Thiago Andrade and Romulo sidelined.
Flamengo possible starting lineup:
Cunha; Franca, Bruno, Luiz, Ayrton; Pulgar, Hugo; Gerson, Ribeiro; De Arrascaeta, Pedro
Athletico Paranaense possible starting lineup:
Bento; Heleno, Henrique, Ivaldo; Khellven, Erick, Moura, Christian; Bueno, Terans; Roque