*Professional career*
*Early career*
Rathbone began his career with Manchester United youth system, having been scouted at the age of seven years old. He made his debut in a pre-season friendly against Shamrock Rovers in July 2014. He also played against Real Madrid Castilla in the same tournament, and started in a 1–0 defeat against Valencia.
On 2 September 2014, Rathbone signed his first professional contract with the club. On 18 December 2014, he made his debut for the club, starting in a UEFA Europa League match against PSV Eindhoven, and was substituted at half-time for Andreas Pereira.
He then appeared for the club in the Football League Trophy against Colchester United on 5 November 2015, playing 90 minutes in a 4–0 win.
*Oldham Athletic*
In March 2016, Rathbone went to League One club Oldham Athletic on a one-month loan to gain first-team experience. He made his Oldham debut on 12 March, starting in a 1–0 defeat against Sheffield United. He scored his first goal on 27 March, in a 3–1 defeat to Bury. He was recalled by United on 1 April after only making two appearances, following the club's involvement in the FA Youth Cup Semi-final second-leg.
On 1 July 2016, Rathbone was released from Manchester United. He returned to Oldham Athletic on 27 July 2016. He made 27 appearances for the club, scoring once in all competitions, helping the club to the semi-final of the EFL Trophy in 2016–17.
*Rotherham United*
On 31 January 2017, Rathbone joined Rotherham United for an undisclosed fee, on a two-and-a-half year contract. He made his debut for the club later that day, starting in a 1–1 draw against Birmingham City. He scored his first goal for the club on 25 March 2017, in a 3–1 League One victory over Rochdale. He made 17 appearances for the club, scoring twice, as the Millers were promoted to the EFL Championship by winning League One.
*AFC Rochdale*
On 2 July 2018, Rathbone joined League One side A.F.C. Rochdale on loan for the 2018-19 season. He scored a brace on his debut in the Carabao Cup against Crewe Alexandra, coming on in the 70th minute to grab two goals in a 3–2 victory. He made a total of 42 appearances for Dale during his loan spell, scoring five times, as they finished in 20th.
*Rochdale*
In May 2019, Rathbone completed a permanent move to Rochdale, joining the club on a two-year contract.