Saprissa enjoyed a 2-0 home win over Uruguay to move them to 32 points, while Herediano fell two points off the pace after Alajuelense cantered to a 5-2 victory.
Armando Alonso and Jonathan McDonald both scored braces for Alajuelense, while Camilo Aguirre added the fifth goal for the rampant winners.
The then-leaders got off to a brilliant start, when Esteban Granados tapped into an empty net on 14 minutes to give the visitors to the Estadio Alejandro Morera Soto the lead.
Verny Scott squared the ball for Granados from the byline, and the midfielder simply had to put the ball on target to score.
McDonald equalised for Alajuelense, netting in the 34th minute after Herediano failed to clear from a set piece.
The Alajuelense forward doubled his tally with a simply chest-in three minutes into the second half.
Alonso got on the scoresheet moments later, as he worked a wonderful one-two with midfielder Alvaro Sanchez before finishing past the on-rushing goalkeeper.
Ten minutes later, it was 4-1 and Alonso had a brace with a straightforward tap-in as the result of a flicked on header from a corner.
Aguirre then curled a lovely left-footed effort from inside the area into the back of the net, before Esteban Ramirez scored a late consolation for the defeated Herediano.
Saprissa were powered to victory by first-half strikes to Manfred Russell and Hanzell Arauz in their win over Uruguay.
Carmelita are just three points behind third-placed Alajuelense, after a 2-0 road win over UCR.
Belen Siglo XXI and Perez Zeledon both won, with the bottom two sides having victories over Santos de Guapiles and Limon respectively.
Belen Siglo XXI won 1-0 on the road, courtesy of Leonardo Adams' late goal, while Fabrizio Ronchetti and Daniel Ramirez both scored for Perez Zeledon.
Puntarenas has a 1-0 win on the road at Cartagines, with the success ensuring they did not go bottom after the cellar-dwellers' success.
