First-half goals from Yendrick Ruiz and Mauricio Nunez sent Marvin Solano's men to a comfortable three points, which is the difference between them and second side Alajuelense.
Alajuelense were in action on Wednesday, comfortably accounting for UCR at home 5-2.
Early goals gave Alajuelense a 3-0 buffer inside 35 minutes, with each of Jerry Palacios, Jonathan McDonald and Ariel Soto getting on the scoresheet.
UCR twice pegged the deficit back to two goals, but each time they did, Palacios and then McDonald scored to see them finish with braces.
Deportivo Saprissa sit third on 19 points, one behind Alajuelense, after a 2-1 win at Belen Siglo XXI.
Saprissa led 2-0 at the half-time break, and had seen Belen Siglo XXI's Ricardo Gonzalez sent off, but they were made to sweat when Daniel Varela scored eight minutes after the interval.
Cartagines climbed into fourth, as their 2-2 draw at home to cellar-dwellers Perez Zeledon was enough to see them eclipse Limon on goal difference - with both sides on 14 points.
Uruguay made it consecutive wins, as a Jonathan Moya double helped them to a 2-0 road triumph over Puntarenas.
The other scheduled clash of the matchday, between Santos de Guapiles and Carmelita, was postponed.
