By Gabriel Pessoa

Copa Libertadores groups are beginning to take shape as clubs return from international break and round three gets underway. Teams who have gotten off to an unfavorable start such as Gremio and River Plate will have to kick it into high gear, while clubs we got to know from way back in the qualifying stage - such as Atletico Mineiro, Deportes Tolima and Melgar - can no longer afford any more slip ups. Taking those high stakes into account, here are five Copa Libertadores matches you should watch this week:

San Lorenzo (ARG) vs. Palmeiras (BRA) – Group F

Tuesday @ 6:05pm ET live on beIN SPORTS (HD ENG)

Defending Brazilian champions Palmeiras have had an impressive start to the season. The club from Sao Paulo sits atop group F after two convincing victories. With all respect to Junior F.C. and Melgar though, this week presents the toughest test to date for Palmeiras, as they travel south to Argentina to take on San Lorenzo.

Like Palmeiras, San Lorenzo are also undefeated at this juncture of the 2019 Copa Libertadores. Argentinean supporters have displayed time and again why they’re considered to be some of the most passionate fans in the world, and the Los Santos faithful is no different.

A victory for the home side would propel San Lorenzo to the top of the group and complicate Palmeiras’ path out of the group.

Athletico Paranaense (BRA) vs. Boca Juniors (ARG) – Group G

Tuesday @ 8:20pm ET live on beIN SPORTS (HD ENG)

The week’s second installation of Brazil versus Argentina comes courtesy of second place Athletico Paranaense hosting group leaders Boca Juniors.

Group G is very much so up for grabs, with one point separating top from third, so despite falling to a defeat on the road to Deportes Tolima last time out, O Furacao can reassert itself with a momentum-generating win over last year’s Copa Libertadores runners-up.

Boca on the other hand, after a disappointing draw against Jorge Wilstermann in its Copa Libertadores opening match, will want to right their wrongs and keep hold of top spot.

Internacional (BRA) vs. River Plate (ARG) – Group A

Wednesday @ 6:05pm ET live on beIN SPORTS (HD ENG)

Libertadores fans rejoice! Wednesday will provide yet another continental rivalry with plenty on the line. The Beira Rio Stadium will be rocking as Internacional hosts defending Copa Libertadores champion River Plate.

River Plate’s Libertadores has not gone according to plan so far. Two draws in two matches and its star midfielder, Juan Quintero, ruptured his ACL. River Plate’s supporting cast will have to rise to the occasion Wednesday against the group A leaders.

Internacional have won both matches thus far and will look to keep that winning streak alive at home. A loss for River Plate would seriously jeopardize their chances of making it out of the group.

Atletico Mineiro (BRA) vs. Zamora FC (VEN) – Group E

Wednesday @ 6pm ET live on beIN SPORTS (Connect 4)

The Libertadores title of 2013 seems like an eternity ago for Atletico Mineiro. Galo have displayed two disappointing performances and for that, the Brazilian club finds itself in last place in group E.

Luckily for Galo, Venezuelan side Zamora have accumulated zero points in the Libertadores as well. Both sides will be desperate for a win to kick start an attempted climb back to the top of the group.

Luckily for us all, the venue for a clash with this much on the line will be the ‘Mineirão’. The same venue where the home team won its only Libertadores title. Expect every seat to be filled and for there to be nearly constant chanting from the fans. A loss for either side could very well mean the end of its hopes of qualifying to knockout stages.

Flamengo (BRA) vs. Penarol (URU) – Group D

Wednesday @ 8:20pm ET live on beIÑ Sports (HD SPA)

This matchup is a quintessential Copa Libertadores game. With six Libertadores titles between these clubs and two of the continent’s most impressive fan bases on either side, we are all truly in for a treat Wednesday evening.

Flamengo lived up to the billing as one of the tournament favorites so far. Led by Diego and Gabigol, the hosts will aim to add make it three consecutive Libertadores group match wins in front of what should be a packed Maracanã.

The traveling Penarol fans will hope for their club to not shy away from the intimidating lights of the hallowed grounds in Rio de Janeiro. A win for the Uruguayan giants can propel Penarol to first in Group D.