GWS will appeal the AFL tribunal's decision to uphold Toby Bedford's one-match suspension in a bid to free the small forward for their elimination final against St Kilda.
Bedford failed to have his one-match rough conduct ban, for an off-the-ball bump on Carlton's Zac Fisher in round 24, overturned or downgraded on Monday afternoon.
The appeal is set to be heard by the AFL appeals board on Thursday afternoon, two days before the MCG final.
The contact was graded as careless, medium impact and high contact, drawing a one-match ban, after Fisher required a concussion assessment at three-quarter time, which he passed.
GWS, relying on evidence from Fisher and a biomechanist, argued the bump was not high or forceful and should not be considered medium impact.
Both of those arguments were rejected by the panel of Jeff Gleeson, Darren Gaspar and Scott Stevens.
"It's disappointing. We thought we had a pretty compelling case," Bedford's teammate Harry Himmelberg said on Tuesday.
"We were of the view that it was a footballing act; he was blocking, it wasn't off the ball."
Bedford has played 16 games in his first season at GWS after he was traded from Melbourne, kicking 10 goals and averaging five tackles per game.