Fremantle ruckman Aaron Sandilands has been taken to hospital with a suspected punctured lung suffered during Saturday night's derby against West Coast.
Sandilands left the field early in the second quarter after copping a knee to the back from Nic Naitanui when the Eagle took a high-flying mark.
After failing to walk off the hit, Sandilands was assessed in the rooms before an ambulance was called.
His absence hurt the Dockers, who slumped to their third loss in succession as the Eagles surged to a 33-point win.
Fremantle coach Ross Lyon confirmed Sandilands had punctured his lung and suffered rib damage.
He also said midfielder David Mundy, who was ruled out before the match with a calf injury, would miss several weeks.
"It's really courageous how he got up," Lyon said of Sandilands.
"It was a big contest. It was a result of a turnover. He got put out of position. It's really disappointing. It's not ideal, but you win them and you wear them."