Tarrant injured his left knee against West Coast at Subiaco Oval on Sunday afternoon.
In a willing contest for the football with Andrew Embley late in the first quarter, Tarrant’s left leg took the full impact of his opponent and he came straight from the ground.
Unaided, the full back walked to Fremantle’s rooms and his day appears over.
Tarrant, who had missed Fremantle’s last five games with an ankle injury, was playing on West Coast forward Mark LeCras, who had been held to no disposals as Fremantle dominated the first term.
Fremantle entered the first break having kicked the first seven goals of the game to build a 45-point lead.
