The AFL should consider introducing a red card system after young Docker Ryan Nyhuis accidentally knocked out Port Adelaide star Robbie Gray with a sling tackle on Sunday at Optus Stadium.

Adelaide forward Josh Jenkins said on Monday he watched the Power go down to Fremantle by nine points in a shock result that severely hampers Port's chances of a critical top-four finals berth.

Robbie Gray is taken from the ground after the tackle from Ryan Nyhuis. Credit:AAP

Gray was knocked out after his head hit the the turf in the tackle by Nyhuis in the third quarter that led to all-in melee, with the 21-year-old reported for rough conduct and referred to the AFL tribunal for a video link hearing in Melbourne via Perth on Tuesday night.

AFL match review officer Michael Christian classified Nyhuis’ tackle on Gray as careless conduct, severe impact and high contact, which meant it was referred directly to the tribunal and carries a minimum sanction of three matches.