An all-star shortstop in the Pacific Coast League, Baker switched to second base as a rookie with the Cubs in 1954 and, along with shortstop Ernie Banks, was named to the all-rookie team by TSN. Although he led NL second basemen in errors for three straight years, he had excellent range and his bat showed occasional home run power. In 1957, Baker was traded to the Pirates along with Dee Fondy for Dale Long and Lee Walls. Early the next season, he injured his knee. He missed all of 1959 and played only a few games in 1960-61 before turning to coaching and scouting for the Pirates.