Ben Long's one-match suspension has been upheld by the AFL tribunal, but St Kilda are likely to appeal the decision in a bid to have the defender available to face Richmond in Friday night's semi-final.
Long was slapped with a one-match ban after crunching Western Bulldogs midfielder Jack Macrae in the first quarter of St Kilda's elimination final win at the Gabba on Saturday.
On Monday, Long pleaded guilty to rough conduct but failed in his attempt to have the charge downgraded from "medium" to "low" impact, which would have reduced the sanction to a fine.
"We are disappointed for Ben and will strongly assess our options for appeal," St Kilda chief operating officer Simon Lethlean said.
"We have until midday Tuesday to submit an appeal and it appears the likely option at this early stage."
Long's ban currently means the Saints will have to make a third forced change to their team to face the Tigers.
Star ruckman Paddy Ryder has returned to Melbourne after suffering a season-ending hamstring tendon injury while Jake Carlisle left their Queensland hub to be with his partner ahead of the birth of their third child.
Long has shone as a defender this year and would be sorely missed against the Tigers' small forward brigade.
AFL match review officer Michael Christian had initially assessed his hit on Macrae as careless conduct, medium impact and high contact and St Kilda only contested the "impact" part of the charge.
After an hour of arguments, then close to half an hour of deliberation, the tribunal jury of Richard Loveridge, David Neitz and Paul Williams upheld the "medium" impact grading.
The jury noted Macrae's head "snaps back on contact" from Long's shoulder, which indicated "clearly more than a glancing contact", while they were surprised the Bulldog had "got up as readily as he did."
St Kilda's legal counsel Jack Rush QC had pointed to the Bulldogs' medical report which said Macrae had required immediate on-field assessment but did not need to leave the field for treatment, there was no need for further investigation or ongoing treatment and he would not have missed any training sessions or matches as a result.
But the AFL's legal counsel Jeff Gleeson QC emphasised Long's momentum and the "significant, forceful impact" behind the bump - and its potential to cause injury - rather than the end result.
The ban is Long's second this season after he previously received a three-match ban for a careless bump which left Fremantle ruckman Sean Darcy concussed in round six.
Apart from those three games, the 23-year-old has played every game for the Saints this year, bringing his career tally to 45.