Arriving in the City of Buenos Aires from just over the River Plate, Uruguayan team Nacional may well have feared the worst having not managed to secure a victory at home in Montevideo in the previous round.
But 20 minutes in, Boca captain Daniel Díaz calamitously sent the ball past his own keeper after a driven cross, putting Nacional into a 2-1 aggregate lead and a precious away goal.
Boca now faced an uphill struggle, needing a goal just to tie the fixture.
25 minutes into the second half after a string of saves by Boca goalie Augustín Orion, striker Cristian Pavón managed to sneak around the back and finish into the bottom left corner.
In the ensuing celebration, Pávon stupidly received a second yellow from Brazilian referee Héber Lopes after taking his shirt off.
Boca was now on tenterhooks, nervously battling to try and secure the victory while knowing that with 10 men, conceding a goal at this stage of the tie would be game over.
Neither team was able to push through the final wall, and without a single minute of added time, the fixture went to penalties.
Up stepped Orion to become Boca’s hero as the Argentines advanced to the semi-finals of the continental competition.
As tense a finish as it may have been, it was nothing compared to Rosario Central’s match against Colombian team Atlético Nacional.
With Rosario holding a 1-0 aggregate lead over its counterparts, it seemed as if it was going to go all its way when forward Marco Rubén scored a 9th minute penalty making it 2-0.
But a magnificent comeback from the Colombians saw them turn the tables in style, culminating with a 95th minute goal. Drama of the highest order as Atlético, who had looked dead and buried, managed to grab the winner.
After some extremely over the top celebrations, naturally, a fight broke out resulting in no less than three red cards, two of them on the Argentine team. Fantastic stuff all round.