Witherden caught Dockers midfielder Andrew Brayshaw flush in the face after opting for a hip-and-shoulder as the pair collided in Fremantle's 11.13 (79) to 10.6 (66) win on Sunday.
Although Brayshaw was able to take the free kick and play out the game, the high nature of the bump could land Witherden in hot water with the AFL's match review panel.
West Coast will already be without Jack Darling, Dom Sheed, Elliot Yeo, Tom Cole, Liam Duggan, Oscar Allen, Jamie Cripps, and perhaps Luke Shuey for round one, so they can ill afford any more absentees.
"Hopefully fingers crossed he's available," Eagles coach Adam Simpson said.
"We probably don't have any more backs to play. We'll work through that."
The Eagles fought hard throughout Sunday's match, with their effort making up for last week's insipid 97-point loss to the Dockers.
Tim Kelly starred for the Eagles with 32 disposals, six clearances and a goal, while Witherden tallied 27 disposals.
Willie Rioli's comeback continues to build momentum, with the forward showing flashes of brilliance in tallying a goal and two score assists from his seven disposals.
Brayshaw finished with a team-high 30 disposals for Fremantle to go with five clearances, while Michael Walters and Matt Taberner booted two goals apiece.
Dockers defender Nathan Wilson hurt his right shoulder while crashing into Witherden's legs in the third quarter, while big man Rory Lobb hurt his ribs and chest after being clattered into by teammate Sean Darcy.Â
"Rory got a knock to the chest. He was a bit short of breath," Dockers coach Justin Longmuir said.
"It's more a bit of soreness. We're pretty confident he'll be right (for round one).
"He wanted to come back on, but we had a talk on the bench, it's just no risk.
"Nathan Wilson got that hit to the shoulder. He's pretty sore and sorry for himself. We have to get it scanned. I'm not going to guess what it is."
West Coast put up more much fight in the first half than they'd shown a week earlier, but there were still some worrying signs.
Sam Switkowski scored the easiest of goals after West Coast's defence went to sleep at a ruck contest in Fremantle's forward 50m.
And there were numerous other times when the Dockers managed to slice and dice their way up the field with ease.
Only Fremantle's inaccurate goalkicking and a star display from Kelly ensured the halftime deficit was only seven points for West Coast.
West Coast's efficiency going forward was a key aspect of the third quarter, with the Eagles booting four goals to two to take a three-point lead into the final break.
But turnovers hurt the Eagles in the final quarter, with two goals and an assist to Walters helping set up the win for Fremantle.
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