Port Adelaide forward Lindsay Thomas will miss the next three weeks after the AFL Tribunal found him guilty of rough conduct against Geelong's Scott Selwood.

The incident occurred during the second quarter of the Power's loss to the Cats on Saturday night, and Selwood was ruled out of the remainder of the game following the hit.

Thomas was referred directly to the Tribunal, after Match Review Officer Michael Christian deemed the contact as careless with severe impact.

All up, Thomas will be unavailable for Port Adelaide's matches against North Melbourne, West Coast and Adelaide.