The Seattle Mariners first closer was Enrique Romo, whom they purchased from the Mexico City Reds out of the Mexican League on April 1, 1977. Romo spent two years with the Mariners before being traded to the Pittsburgh Pirates, where he helped them win the World Series over the Baltimore Orioles in 1979. In his two years with the Mariners, he pitched in 114 games with a record of 19-17 and an ERA of 3.25 over the course of 211 innings.
The Mariners had four other pitchers who appeared in at least 40 games, mostly working out of the bullpen in 1977.