Farrell came on as a substitute in the second half of the 2023 A-League Men Grand Final. Within fifteen minutes of coming on, Farrell earned two penalties for the Mariners, both of which were scored by Jason Cummings as the Mariners won 6–1 to claim the A-League Men Championship.[6]
On 1 May 2024, Farrell scored with a header in an eventual 2–0 win over Adelaide United to secure the 2023–24 A-League Men Premiership for the Mariners.[7] Five days later, Farrell played in the Mariners win in the 2024 AFC Cup final.[8] Farrell played a full game for the Mariners in their win in the 2024 A-League Men Grand Final and set up a late goal for Ryan Edmondson to seal the victory for the Mariners' third trophy of the season.[9]
Portsmouth
On 26 July 2024, Farrell joined English Championship club Portsmouth for an undisclosed fee, signing a four-year deal.[10]