Marino struck within a minute after being sent on in place of Nicolas Gaitan, who had stood in for the suspended Juan Roman Riquelme, by coach Alfio Basile.
The midfielder headed home a corner in the 46th minute and added his second in the 51st with a shot from 30 metres that went in at the base of the near post.
Argentinos had stunned Boca's packed Bombonera stadium in the first half with headed goals from forwards Gabriel Hauche and Nicolas Gianni as the Apertura championship began a week late.
River Plate, Boca's arch-rivals, fared worse, going down 2-0 at Banfield with a line-up that appears over-reliant on old hands Ariel Ortega and Marcelo Gallardo, both well into their thirties.
Paraguayan Santiago Salcedo, signed from Newell's Old Boys during the off-season, scored both goals for Lanus, who did not miss striker Jose Sand, last season's leading scorer who has moved to Al Ain in Abu Dhabi for $10 million.
"A team is the product of training sessions, not improvisation," Cappa was quoted as saying.
"We practised on Friday afternoon with the team that was going to play (on Sunday) and that night three players had to drop out because the transfers hadn't been completed so we had to improvise on the spot."
