[3][4] Statistical website BoxRec rates Walker as the 6th best boxer to have ended his career at middleweight, while The Ring Magazine founder Nat Fleischer placed him at No.

[7] Walker boxed professionally for the first time on February 10, 1919, fighting Dominic Orsini to a four-round no-decision in his hometown of Elizabeth, New Jersey.

By then, Rhode Island had become one of the areas where decisions from points scoring had been legislated and this attracted Walker.

He also met world champion boxer Jack Britton in a no-decision in New Jersey and beat Nate Siegal in Boston.

He defeated Lew Tendler and Bobby Barrett in defense of his world title and had two of his three no-decisions that year against Jock Malone.

After winning two fights to start 1925, he went up in division to challenge world middleweight champion Harry Greb on July 2 but failed to win the middleweight crown at that time, losing a fifteen-round decision to the 160-pound (73 kg) division champion.

He went back to the welterweight division, defending his title against Dave Shade and retaining it by decision.

On June 19, 1931, Walker decided to vacate his world middleweight title and move up to the heavyweight division.

In 1932, he went 5–1, beating such fighters as King Levinsky and Paulino Uzcudun before facing former world heavyweight champion Max Schmeling, who knocked Walker out in round eight.

He went down in weight again, to the light heavyweight division in 1933, when he lost a fifteen-round decision to Maxie Rosenbloom for the world title.

Undaunted, Walker kept campaigning in that division until 1935, when he retired after losing to Eric Seelig by a seven-round technical knockout.