FREMANTLE star Luke Jackson will miss Saturday night's AAMI Community Series clash with Port Adelaide after experiencing delayed concussive symptoms this week.
Wingman Nathan O'Driscoll, meanwhile, will join Michael Frederick (hamstring) on the sidelines after suffering inflammation and swelling over his knee following the Dockers' match simulation against West Coast on Saturday.
Jackson was involved in a collision with West Coast midfielder Reuben Ginbey early in Saturday's clash at Mineral Resources Park, which resulted in the Eagles onballer being placed in concussion protocols.
The Dockers assessed Jackson at the time and he was cleared to play, but the forward/ruck experienced a delayed concussive symptoms on Monday and was sidelined for Tuesday's main training session.
"Luke was fine on Saturday night and Sunday but experienced a delayed onset headache on Monday afternoon that worsened as the day went on," football boss Joe Brierty said on Tuesday.
"He has been placed into the concussion protocols and is progressing well."
Jackson played predominantly as a key forward against the Eagles and provided some ruck support to Sean Darcy, with Matt Taberner and pre-season recruit Pat Voss looming as replacement options if the Dockers want to maintain a three tall forward structure. Medium forward Sam Sturt could also be called on.
O'Driscoll, who has been a leading contender for a wing role in round one, will be sidelined for the short term and pulling up with a "significant amount of swelling and inflammation over his knee" following Saturday's clash.
"There is no significant structural damage to the knee joint, but we will wait for the inflammation to subside, and he will be transitioned back into football," Brierty said.
"At this point, we have no clear timeline on his return to play, although we are hopeful it will be short-term."
Frederick's hamstring complaint is minor, while the Dockers were planning for wingman Jeremy Sharp to return and fill a wing role against the Power after being sidelined at the weekend with illness.
The Dockers are growing confident that key defender Brennan Cox will be available for round one after progressing to on-field running on Tuesday as he recovers from a stress fracture in his fibula.
