A 1-1 draw at Cerro Porteno in May enabled the Chileans to finish second in Group A, while Los Quilleros topped Group D with a 0-0 result versus Botafogo.
Match preview
By the thinnest of margins, Colo-Colo advanced into the round of 16 for the first time since 2018, finishing above Cerro Porteno with one more away goal in the group phase (3-2).
Jorge Almiron's side will enter this encounter in fine form, unbeaten in eight consecutive domestic fixtures, playing to a 0-0 draw with Universidad de Chile on Saturday.
Eterno Campeon, however, lost their previous home contest in this competition versus Fluminense 1-0, the only goal they conceded at Estadio Monumental David Arellano in the opening phase.
Their last four competitive fixtures in Macul ended in a victory for Colo-Colo, with the previous three being by just a single goal.
It has been just over six years since this club made it to this stage of the competition, and they have not been knocked out in a Copa Libertadores round of 16 tie since 2007 (4-2 on aggregate versus Club America).
Los Albos have not won a Copa Libertadores fixture against a Colombian opponent since the 2003 group stage, when they defeated Independiente Medellin 2-1.
Junior have waited a long time to qualify for the knockout phase of this competition, with their previous appearance occurring in 2011.
Although they failed to win twice in the group stage when scoring first, Arturo Reyes still saw his side go undefeated, finishing above Botafogo on goal difference.
Seven of their 10 points claimed in the group stage took place away from home, with Junior claiming a 1-0 triumph over LDU Quito in mid-May.
The reigning Finalzacion champions in Colombia have not won a round of 16 fixture at the Copa Libertadores since defeating Cerro Porteno 1-0 in 1996, advancing from that tie by that narrow margin.
Coming into this encounter, the Colombians are riding a three-match unbeaten run across all competitions, playing to a 2-2 draw with Alianza in their previous game.
Los Tiburones will have fond memories of their last visit to Estadio Monumental David Arellano, scoring twice in the second leg of that round of 16 tie to claim a 2-2 draw and advance into the 1994 quarter-finals on penalties (6-5).
Colo-Colo Copa Libertadores form:
W
L
D
L
D
D
Colo-Colo form (all competitions):
Atletico Junior Copa Libertadores form:
W
D
D
D
W
D
Atletico Junior form (all competitions):
Team News
In their 0-0 draw with Universidad de Chile this past weekend, Colo-Colo were without Alan Saldivia because of a meniscus tear, and Cesar Fuentes sat out due to a cruciate ligament tear.
A 23rd-minute penalty converted by Carlos Palacios was all they could manage in their previous Libertadores fixture against the Paraguayans.
From matchday five to six in this competition, Junior brought in five newcomers to their starting 11, including Edwin Herrera, Howell Mena, Gabriel Fuentes, Homer Martinez and Deiber Caicedo.
Uruguayan goalkeeper Santiago Mele has posted consecutive clean sheets in this tournament and did not have to make a single stop in their draw with Botafogo.
Colo-Colo possible starting lineup:
Cortes; Opazo, Amor, Falcon, Wiemberg; Castellani, Pavez, Pizarro; Bolados, Palacios; Paiva
Atletico Junior possible starting lineup:
Mele; Herrera, Mena, Olivera, Fuentes; Moreno, Velez, V. Cantillo; Enamorado, Rodriguez, Caicedo
We say: Colo-Colo 0-0 Atletico Junior
It has been a while since either side have been involved in a game of this magnitude, and we expect both teams to be timid and play to avoid defeat rather than win.