Oscar Ramirez's Alajuelense have already booked their place in the semi-finals, and made it back-to-back wins with a 2-1 victory over Limon.
Pablo Gabas scrambled in a fifth-minute opener and Alvaro Sanchez tucked away a finish at the back post early in the second half.
Henry Cooper's 58th-minute goal proved to be mere consolation.
Herediano climbed into second with a 6-2 thrashing of Uruguay.
Yendrick Ruiz scored a hat-trick as Herediano netted six times in the final half-hour of a come-from-behind win.
Deportivo Saprissa failed to win for the third time in their past four league matches, going down 2-0 at UCR.
Cartagines are a point adrift of fourth-placed UCR and edged Santos de Guapiles 1-0.
Carmelita struck twice late on to beat Puma Generalena 3-2 and Perez Zeledon drew 1-1 with Belen Siglo XXI.
