Fremantle have lost ruckman Sean Darcy to a concussion before half-time of their blockbuster clash against Collingwood at Adelaide Oval on Friday night.

Darcy was lifting himself up after he picked up the footy deep in defence when his head hit the shoulder of Magpie Ned Long.

The big man was visibly rattled as he got up off the ground and was taken straight from the ground in the hands of the trainer.

Darcy’s unfortunate injuries comes as calls continue for former Collingwood bigman Mason Cox to make his Dockers debut after crossing on a two-year deal after he was delisted by the Magpies.

It has left Luke Jackson to ruck solo against Collingwood pair Darcy Cameron and Oscar Steene with either Pat Voss or Josh Treacy to back him up.

Collingwood are also down to 22 men with star Jordan De Goey ruled out after he failed a concussion test following an incident in the first term.

Cox has been named to play for Peel Thunder against Claremont at Revo Fitness Stadium tomorrow.

He is now likely to make his debut for the Dockers in the western derby clash against West Coast next Sunday.

More to come...