Port Adelaide's AFL premiership defence has hit a sizeable speed hump, suffering three mid-term injuries and facing the loss of a star player through suspension.

The Power's 13.10 (88) to 7.11 (53) loss to Fremantle in AFL round one on Saturday night was soured, with Peter Burgoyne, Shaun Burgoyne, Toby Thurstans and Josh Mahoney all likely to be out for several weeks.

Those absences came at a bad time for the premiers, facing upcoming games against Brisbane, the SA derby against Adelaide, Carlton and then premiership threat Geelong.

Peter Burgoyne was reported for rough play relating to a spear tackle on ex-teammate Josh Carr, who was making his Freo debut after defecting from Port.

Having been suspended for a spear tackle on West Coast's Daniel Kerr in 2003, Burgoyne would face at least a two-game suspension on this charge, even allowing for a guilty plea.

Burgoyne lifted Carr in the tackle as Power captain Matthew Primus simultaneously tackled Carr around the upper body, creating a tilting motion that saw Carr driven head-first into the ground.

That created a possible defence for Burgoyne, as his actions partly contributed rather than wholly caused the spear tackle.

Even with a multiple-game suspension, Burgoyne was likely to be back in action before his brother Shaun, who damaged the posterior cruciate ligament in his left knee.

His knee buckled sideways in a kicking motion, and will now miss at least four and as many as six weeks.

An identical absence was faced by Mahoney, who damaged a medial knee ligament, interrupting his fairytale story of being vaulted from AFL discard to VFL journeyman then back to AFL premiership player.

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