He also had a standout national carnival representing Vic Metro in the TAC Cup, earning All-Australian selection in his final year of junior footy.

Coffield made his debut in the forty-nine point loss to Adelaide at Etihad Stadium in round three of the 2018 season.

[2] In April 2018, Coffield and fellow 2017 draftee Hunter Clark extended their contracts with St Kilda until the end of 2021.

[5] His season ended early after suffering a dislocated shoulder in St Kilda's Round 21 match against Fremantle.

Despite the shortened season and quarters, Coffield established himself a prominent defender who averaged over 15 disposals and six marks a game.