Penarol hammered in Libertadores opener
Jackson Martinez scored a hat-trick for the Colombians in Wednesday night's preliminary round, first leg tie in Medellin, leaving the Uruguayans almost certain to miss out on the group stage.
Martinez headed in from a corner in the 15th minute and scored again four minutes later as he snapped up a rebound.
Ivan Corredor's free kick gave Medellin a 3-0 halftime lead and Martinez completed his hat-trick two minutes after the break.
Penarol, eliminated in the preliminary round on their last Libertadores appearance in 2005, were once a major force in South America but have faded badly over the last few years.
Uruguayan domestic football suffers from chronic financial problems due to the country's small internal market and an exodus of players to foreign clubs.
Former Oman coach Ribas, a firebrand who once spent eight days in jail for his part in a brawl on the field, was appointed by Penarol for a second stint earlier this month.
Marcelo Diaz scored an early goal to give Universidad de Chile a 1-0 win over Mexico's Pachuca in Wednesday's other tie.