Hacker was a base coach in the Major Leagues from 1986 to 1993, coaching for the St. Louis Cardinals from 1986–90 and the Toronto Blue Jays from 1991-93. Hacker coached first base for the Cardinals from 1986–87 and third base from 1988-90. He was the third base coach for the Blue Jays from 1991-93. He coached in two World Series (1987 and 1992) and was on the Blue Jays bench for a third (1993). He also coached in the 1988 Major League Baseball All-Star Game. His Major League coaching career was ended by a car accident suffered on the Martin Luther King bridge in St. Louis in July 1993. During his recovery from injury he remained a member of the Blue Jays coaching staff, but was transferred to off-field work such as creating hitting charts of opposing teams. He was replaced as third base coach by Nick Leyva.
Hacker is currently enjoying retirement with his wife Kathryn and three grown children, Roger, Scott, and Katy, in Belleville, Illinois. He remains an active hunter and amateur baseball scout. He is part of the New Athens High School Hall of Fame.