Born in Blackpool,[2] Crellin moved on loan from Fleetwood Town to FC United of Manchester in August 2018,[3][4] but was recalled early in September 2018.

[8] His debut came on 5 September in Bolton's first match of the season, a 1–2 home defeat against Bradford City in the first round of the EFL Cup.

[9] On 28 September Crellin was defended by Bolton head coach Ian Evatt after being criticised for perceived errors in games.

[14] Crellin continued to make mistakes however[15] and on 13 November he was dropped to the bench for Bolton's derby match against Salford City.

[17] On 31 January 2022, Crellin joined Everton for an undisclosed fee on a two-and-a-half-year deal, linking up with their under-23 squad.