Ronald Gonzalez's Deportivo Saprissa side claimed their fourth straight win with a 3-0 victory over UCR at the Estadio Ernesto Rohrmoser Lahmann.
David Ramirez, Ariel Rodriguez and Michael Umana were on the scoresheet as Deportivo moved a point clear at the top.
Herediano drew 1-1 at lowly Puntarenas, who are second bottom with just two league wins from 13 matches.
Saprissa took a 54th-minute lead away from home as Ramirez chipped a stranded Carlos Mendez to make it 1-0.
The visitors needed another 25 minutes to double their lead as Rodriguez scored his sixth league goal of the season as he tapped in after UCR gave away possession poorly.
Umana sealed the points from the penalty spot on 89 minutes.
At the Estadio Lito Perez, Herediano took the lead on the hour-mark.
Yendrick Ruiz delightfully flicked in a cross, but the visitors were unable to hold on for three points.
Daniel Quiros' scrappy equaliser 10 minutes from full-time snatched a point for Puntarenas, who are winless in their past six matches.
Alajuelense slipped seven points behind the leaders after a surprise 4-2 loss at Limon, while Santos de Guapiles and Uruguay drew 1-1.
Carmelita and Cartagines also played out a 1-1 draw.
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