Primarily a second baseman and shortstop, the right-handed hitting and throwing Krol never reached the Major Leagues during his playing career (1954–1966). 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, however, he was managing at the Triple-A level in the St. Louis system, and he received his Major League baptism as a Cardinals coach in 1977. He served 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 (1981–1986) (serving on Dick Williams' staff in 1984 when the 1984 Padres won the National League pennant) and minor league manager (1987–1990). Krol returned to the Cardinals as manager of the Triple-A Louisville Redbirds in 1992–1993. Over his 17-year minor league managerial career, he won 1,160 games and lost 1,139 (.503) and won three championships.
- Howard M. Balzer, ed. The Baseball Register, 1980 edition. St. Louis: The Sporting News.