After his playing career he was a pitching coach for the Los Angeles Dodgers, New York Mets, Boston Red Sox, Houston Astros and Baltimore Orioles.

An all-around athlete at Sacred Heart High School of Waterbury, Connecticut, Wallace played baseball, basketball and football.

After his retirement as a player, Wallace became a pitching coach in the Dodgers' organization for Class A Vero Beach (1981–82), Double-A San Antonio (1983) and Triple-A Albuquerque (1984–86).

But he and Valentine did not have a close working relationship,[2][3] and Wallace resigned after the 2000 World Series to rejoin the Dodgers as senior vice president, baseball operations.

Wallace left the Dodger front office to become the pitching coach for the Boston Red Sox on June 10, 2003, replacing Tony Cloninger, who at the time was (successfully) battling bladder cancer.

In February 2006, while driving to spring training, Wallace was hospitalized in Spartanburg, South Carolina, with intense pain in his right hip.