Boca Juniors claimed a 4-2 penalty shootout win over Lanus on Saturday to reach the Argentine Apertura tournament quarter-finals, following a tense 0-0 draw under a cloud of fan dissatisfaction at the La Bombonera stadium.
Boca goalkeeper Agustin Marchesin, who was pivotal in preserving the deadlock during the match, gave Boca an early advantage in the shootout by saving Alexis Canelo's opening kick.
Lanus winger Dylan Aquino then blazed a shot over the bar while Boca held their nerve, converting their first three penalties with confidence.
Substitute Milton Gimenez stepped up to convert the decisive spot-kick, sealing Boca's place in the next round where they will meet either Independiente or Independiente Rivadavia.
Despite the win, the mood at La Bombonera was far from festive, as local fans voiced their frustration with a series of underwhelming performances, directing chants at both the players and club management, Reuters reported.
"We definitely need to improve, but we achieved what we wanted to achieve, which was to get through the round. From here, we now have to work to improve," interim Boca coach Mariano Herron, who replaced sacked coach Fernando Gago last month, told reporters.
"We understand the fans' anger. We need to work to improve, but it's understandable that they weren't satisfied."
On the pitch, the match itself was low on quality, with neither side managing to assert dominance or create significant scoring opportunities.
Lanus had the best chance of the first half, with Ramiro Carrera's powerful long-range effort just before halftime, but Marchesin was on hand to make a crucial save.
"Fans can tell you how the match is going," Lanus captain Carlos Izquierdoz told ESPN.
"We attacked, we were well positioned, and the fact that their fans started to jeer means that we were doing things right. We were confident."
The Boca goalkeeper, however, continued to thwart Lanus, denying Marcelino Moreno early in the second half and making a series of interventions to keep the scoreline level, setting the stage for Boca's successful penalty shootout.
In the other Saturday last 16 fixtures, San Lorenzo secured a dramatic 2-1 win over Tigre, while Rosario Central made the most of their home advantage to knock Estudiantes out with a 2-0 victory.
Platense pulled off a major upset by claiming a late 1-0 win at Racing Club.