Fremantle ruckman Aaron Sandilands was taken to hospital with a suspected punctured lung during his side's 33-point loss to the Eagles in Saturday night's western derby at Domain Stadium.
Sandilands left the field early in the second quarter after copping a knee to the back while standing under Nic Naitanui's high-flying mark.
After attempting to walk off the pain, Sandilands was assessed in the rooms before being taken away in an ambulance.
His absence left 15-game utility Alex Pearce as the Dockers' lead ruck option.
Fremantle led by eight points when Sandilands went off injured, and they only trailed by five when Matthew Pavlich kicked two quick goals midway through the final term.
But West Coast held their nerve to secure the 12.20 (92) to 8.11 (59) win, with recruit Lewis Jetta booting the settler before the Eagles ran rampant in the dying minutes.
Matt Priddis won the Ross Glendinning medal as best afield in his 200th match, with the Eagles' midfielder tallying 31 disposals and 10 clearances.
The result leaves Fremantle's premiership hopes hanging by a thread.
The Dockers are winless in three games, and face premiership hopefuls North Melbourne next week at Etihad Stadium.
Not since the Kangaroos in 2007 has a side reached the top eight after opening their season with three straight losses.
Simple errors were the running theme throughout the match, with both sides guilty of committing horror turnovers.
Fremantle made the most of their chances to take an eight-point lead into quarter time.
The second term threatened to be a goalless affair before Eagles defender Eric Mackenzie banged through a long-range goal in the dying minutes of the half.
Jack Darling added another shortly after to give West Coast a six-point buffer at the long break.
Vision of Sandilands wearing an oxygen mask while being escorted into the ambulance at halftime would have left Dockers coach Ross Lyon with a sinking feeling.
And a heavy downpour during the break meant Pearce would face even more stoppages against West Coast ruck duo Naitanui and Scott Lycett.
When Pearce was unavailable for ruck duties, Fremantle were forced to turn to plans C, D and E.
Matt de Boer (186cm) and Michael Barlow (189cm) were among the Docker players thrown into the ruck rotations, and they did well to ensure Naitanui didn't dominate entirely.
West Coast finally wore the Dockers down during the third quarter, and the game would have been iced early in the last had the Eagles made the most of their opportunities in front of goal.
But those misses - combined with one of the great derby goals by Pavlich - pulled Fremantle back into the match.
Pavlich kept the ball in play in the pocket while evading an opponent, and then nailed his banana kick from the tightest of angles to breathe life into the Dockers' victory hopes.
And when he nailed another goal shortly after, the margin was just five points with plenty of time left.
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."
West Coast coach Adam Simpson was happy with the win, but said his team's inaccuracy could have proved costly.
"We definitely could have converted a bit better," Simpson said.
"We like to give our forwards plenty of supply. Normally if you get over 60 inside 50s, we normally go pretty well.
"The fact we didn't finish off is disappointing, but I think, in general, we grinded it out pretty well."
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