Fluminense got through to the last eight by beating Gremio on penalties in the round of 16, while Atletico Mineiro overcame Argentine Primera Division outfit San Lorenzo 2-1 on aggregate.
Match preview
After a memorable last season, which saw them win the Copa Libertadores for the first time in the club's history, Fluminense have experienced a significant drop off this season, particularly in their domestic league campaign.
Currently sat one spot above the dotted line in Brasileiro with just 27 points after 25 matches, O Flu's only hope of qualifying for the Libertadores next season now hinges on their ability to win the title again this term.
Fluminense's turbulent season led to the club opting to part ways with Fernando Diniz after two years at the helm with Mano Menezes brought in to steady the ship, and under his stewardship, there has been some improvement noted, with the new boss posting a record of seven wins, four draws and five losses in his first 16 games in charge.
That said, the hosts did lose their first match back from the international break, beaten 2-1 by Juventude after taking a 1-0 lead, ending a four-match unbeaten run in all competitions in the process.
However, O Flu will enter this contest with the psychological advantage, having beaten this opponent 2-0 on the road less than a month ago in a league encounter.
Like O Flu, Atletico Mineiro also underwent a change of leadership this season, with the team bidding farewell to Luiz Felipe Scolari at the start of the season and replacing him with Argentine Gabriel Milito.
While not as severe as Fluminense's league capitulation, Galo have also experienced a notable dip in form this season, currently in 10th place in Brasileiro after finishing third in the league standings last term.
In the group stages of this competition, they managed a record of three wins, one draw and two losses to qualify for the knockout alongside Athletico Paranaense, before getting by San Lorenzo with a 1-0 victory in their home leg in the round of 16.
However, since the international break, Galo have yet to find their rhythm, drawing goalless in the Copa do Brasil with Sao Paulo before suffering a 3-0 defeat to Bahia in the league on Saturday night.
That defeat also ended Atletico Mineiro's four-match unbeaten run on the road and was the third time in their last five league games they failed to find the back of the net.
Fluminense Copa Libertadores form:
D
W
W
W
L
W
Fluminense form (all competitions):
L
D
W
W
W
L
Atletico Mineiro Copa Libertadores form:
W
W
L
W
D
W
Atletico Mineiro form (all competitions):
W
L
W
W
D
L
Team News
Fluminense are set to be without the services of three players for this first-leg quarter-final matchup with Lele, Diogo Barbosa and Ignacio all ruled out of the contest due to injury.
Jhon Arias has been in excellent form for O Flu of late, netting in three of their last four games, and should almost certainly start alongside Kaua Elias as part of the two-man frontline in this one.
Atletico Mineiro, meanwhile are expected to be without four players here, starting with Matias Zaracho, who has been ruled out for the remainder of this season following a hernia operation.
The other absentees for Galo include Alisson (hamstring), Eduardo Vargas (calf) and Otavio (shoulder), though the latter is expected to make a full return before the second leg at the end of this month.
Fluminense possible starting lineup:
Fabio; Xavier, Silva, Santos, Marcelo; Bernal, Nonato, Ganso, Serna; Arias, Elias
Atletico Mineiro possible starting lineup:
Everson; Saravia, Battaglia, Alonso, Arana; Vera, Franco, Scarpa, Bernard, Vargas; Deyverson
We say: Fluminense 2-1 Atletico Mineiro
While Fluminense have been some way from their best this season, they have managed to pull off results in this competition when it mattered. Additionally, the hosts beat this opponent less than a month ago and are unbeaten in their last seven games at home. Thus, we feel O Flu will edge the result in this one.