After impressing in the first five games of the season, the two-time North Launceston premiership star had his leg pinned beneath an opposition player in the first quarter of the round six loss to Essendon.

The 20-year-old played out the game to finish with 13 touches but could not recover for last round's loss to Richmond.

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"The specialists advised intervention was necessary on this occasion," North Melbourne football general manager and fellow Tasmanian Brady Rawlings said.

"It's very unfortunate for Tarryn and for the team, but we always make decisions based on professional opinion, and with the long-term health and well-being of our players front of mind."

A former St Patrick's College student, Thomas was drafted with pick eight - one above Launceston-turned-Adelaide star Chayce Jones - in the 2019 national draft.

He has played 26 games for a return of 19 goals.