Winners of the first stage, Herediano struck twice in the second half in their 2-0 over Cartagines at the Estadio Jose Rafael Fello Meza.
Jorge Arias was on the scoresheet from the penalty spot and Victor Nunez struck soon after to give Herediano a huge advantage heading into the return leg.
Arias' 57th-minute opener via a spot-kick came after Esteban Sirias was sent off for the home side.
Nunez doubled the lead seven minutes later before he too was red-carded in the dying stages.
Deportivo Saprissa edged past Alajuelense 1-0 at the Estadio Ricardo Saprissa Ayma in San Jose.
Just after the hour-mark, Deyver Vega scored the only goal of the game with Alajuelense having been reduced to 10 men earlier when Allen Guevara saw red for lashing out.
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