Deportivo Quito defeated Emelec 1-0 away from home to hold a narrow advantage going into the second leg of the Ecuadorian Serie A final.
Fidel Martinez scored the only goal of Monday s first leg at Estadio George Capwell in Guayaquil.
The right midfielder caught Emelec goalkeeper Wilmer Zumba off guard with a snap shot 30 minutes into the match.
Emelec are likely to be up against it in Sunday s return, when Deportivo will hold a narrow lead on home soil in Quito.
Deportivo are looking to secure their fifth national title, and third since 2008, while Emelec are bidding for an 11th championship crown.