Isales made his MLB debut on September 11, 1980, when he was inserted into the game as a pinch runner for Pete Rose in the top of the ninth inning; he was replaced in the bottom of the inning by Phillies' closerTug McGraw in the Phillies 5–1 victory over the New York Mets at Shea Stadium.[2] His first at bat came on September 30, when he hit a 2-RBI triple as the Phillies defeated the Chicago Cubs at Veterans Stadium.[3] In Isales' final game, manager Dallas Green named him as a starter in right field; he played the entire game which the Phillies lost in the bottom of the tenth inning, 7–8, to the Montreal Expos at Olympic Stadium.[4]