As an amateur, Crocker fought out of the Cairn Lodge Boxing Club in Belfast before eventually moving to Holy Trinity in the west of the city.

The UBC did not select Lewis to represent Ireland in the 2015 Commonwealth Youth Games despite a recommendation by the Irish Amateur Boxing Association's head coach for Ulster.

Lewis believed he was not picked for the NI Commonwealth Youth Games squad because of his Protestant background or perceived unionist political opinions.

[10] Crocker made his professional debut on 10 March 2017, scoring a first-round technical knockout (TKO) victory over Ferenc Jarko at the Waterfront Hall in Belfast.

[11] Crocker is scheduled to face Paddy Donovan in a final eliminator for IBF welterweight title on March 1, 2025 at SSE Arena in Belfast, Northern Ireland.