Primarily a second baseman and shortstop, the right-handed hitting and throwing Krol never reached the Major Leagues during his playing career (1954–66).

The native of Chicago, Illinois, spent most of that period in the St. Louis Cardinals farm system, and became a playing manager in 1966 with the Rock Hill, South Carolina, franchise of the Class A Western Carolinas League.

By 1972 he was managing at the Triple-A level in the St. Louis system, and received his Major League baptism as a Cardinals coach in 1977, working on the Redbirds' staff through 1980 and twice served as interim manager (in 1978 and 1980), winning one game and losing two.

Krol then joined the San Diego Padres as a Major League coach (1981–86) and was a member of the staff of Dick Williams when the 1984 Padres won the National League pennant.

In his memory, the Padres created the Jack Krol Award, which annually honors the club's top player development personnel.