Defensor Sporting and Olimpia played out a frustrating 0-0 draw in the first leg of their Copa Libertadores first stage tie on Thursday.
Uruguayan side Defensor, who finished third in the Primera Division last season and sit second halfway through this campaign, had their chances.
Ignacio Risso squandered two decent opportunities, putting both over the bar as his side were unable to find a breakthrough at Estadio Luis Franzini.
It leaves Defensor with a big task heading into the second leg in Asuncion on January 31.
Elsewhere, Deportes Tolima recorded a 1-0 win over Universidad Cesar Vallejo in the first leg of their tie.
The Colombian outfit hosted the first leg and were victorious thanks to Rogerio Leichtweis' 58th-minute goal at Estadio Manuel Murillo Toro. Carlos Castro's side held onto their advantage despite midfielder Breiner Belalcazar being sent off after picking up a second yellow card on the hour mark.
They will take a one-goal lead into the second leg, which will be played in Peru on January 31.