Goals to Johan Condega and Andres Lezcano saw Cartagines defeat Deportivo Saprissa 2-1, leapfrogging the vanquished side into third in the standings and claiming an unassailable five-point advantage of fifth-placed UCR.
It means the Torneo de Invierno semi-finalists are confirmed heading into the final round of the regular season, which will be held on Sunday.
Condega's free-kick in the ninth minute put Cartagines on the way to victory, while Lezcano made it 2-0 three minutes after half-time, although he was given a helping hand by Saprissa's goalkeeper, who let the long-range strike slip through his fingers into the net.
The win took Cartagines to 39 points, one ahead of Saprissa, while UCR's (34) hopes of reaching the semi-finals are dashed.
