He played in Major League Baseball (MLB) from 1970 to 1982 for the St. Louis Cardinals, Kansas City Royals, and Atlanta Braves.

At the age of twenty, he made his Major League debut with a scoreless inning against the San Diego Padres on June 16, 1970.

Hrabosky led the National League in saves in 1975 with 22 (a career-best) en route to winning The Sporting News "NL Fireman of the Year" award.

Early in his career with the Cardinals, Hrabosky enhanced his menacing appearance with long hair and a horseshoe moustache.

When Vern Rapp became Cardinals manager in 1977, he imposed a grooming code on the players; Hrabosky cut his hair and shaved the moustache despite his vehement opposition.

"[5] The enmity between Hrabosky and Rapp persisted throughout the season and included the former being suspended on May 21 for what Cardinals management stated as "rank insubordination.

As the Redbirds home crowd roared, Hrabosky went into his "Mad Hungarian" routine and proceeded to strike out right-handed power hitters George Foster, Johnny Bench, and Bob Bailey.

[8][9] Hrabosky was traded from the Cardinals to the Kansas City Royals for Mark Littell and Buck Martinez during the Winter Meetings on December 8, 1977.

Hrabosky signed with the Chicago White Sox during spring training in 1983, but retired before the season began.