Hopkin's contract with Manchester United resulted in the club being fined £350, having illegally offered him more than the league maximum wage plus a percentage of his transfer fee.

Hopkin had to wait until 3 March 1923 for his debut goal, when he scored in the 49th minute of Liverpool's 3–0 home win against Bolton Wanderers.

Less than a year after joining Liverpool, Hopkin was celebrating a league title as the team finished with 57 points, six more than second-placed Tottenham Hotspur.

Hopkin remained a regular starter for the club and quickly put together 360 appearances for Liverpool, it helped his cause that he stayed relatively injury-free during his time at Anfield.

Hopkin was allowed to leave Liverpool in 1931, and he rejoined Darlington for a second spell, this after playing 360 times for the Reds, scoring just 12 goals.