MacCormack, who made his MLB debut a season earlier with nine appearances with the Detroit Tigers, played in three games for Seattle in their inaugural 1977 campaign, not factoring in a decision while posting and earned run average of 6.31 over 7 innings of work.
Turns out, those would be the last appearances of his Big League career as he would spend the next two seasons in the Minor Leagues playing for Seattle and Detroit, retiring at the age of 24 after 1979.
All told, he finished his career with a record of 0-5, posting an ERA at 5.45 over 12 appearances and 39.2 innings pitched.