Carlton captain Patrick Cripps will miss the Blues' crucial final two regular-season games after failing to overturn his rough conduct charge at the tribunal.
The Blues were desperate to have their star midfielder available for season-defining matches against Melbourne and Collingwood.
But the tribunal upheld Cripps' two-match ban for bumping Brisbane's Callum Ah Chee, with his bump leaving the Lion concussed.
The match review officer graded the incident as careless, high impact and high contact.
"In a different era that would not have resulted in a report, but in the current era under the current rules and guidelines, this issue is not straightforward," AFL chairman Jeff Gleeson said.
"(Cripps) entered the contest at speed, he saw a player at least in his peripheral vision and leapt into the contest.
"Cripps could, and should, have contested the ball differently and in a way that did not present such a high and serious risk to his fellow player."
Cripps earlier said he wanted to take possession, rather than cause damage to Ah Chee.
"No way I can contest that ball without a collision being there," the Blues midfielder told the tribunal.
"In the heat of battle when the ball's there to be won, I'm going to try and take possession of the ball."
Fellow Carlton star Sam Walsh, an emerging leader, expected fullback Jacob Weitering to fill-in as captain for Cripps when speaking earlier on Tuesday.
Currently seventh on the ladder with a 12-8 record, the Blues will need to win one of the two matches to secure the club's first finals spot since 2013.
Carlton could still sneak into the top-eight if they lose to both the Demons and the Magpies, but would have to rely on St Kilda and the Western Bulldogs stumbling.
Meanwhile, West Coast midfielder Tim Kelly will miss Saturday night's western derby against Fremantle after failing to overturn his one-game ban at the tribunal.
Kelly was charged by the match review officer for a dangerous tackle on Adelaide youngster Sam Berry in the Eagles' loss at Optus Stadium on Sunday.
Berry was unhurt in the incident but the tackle was still graded as careless conduct, medium impact and high contact.
The Eagles (2-18) will already be without retired forward Josh Kennedy, who booted eight goals in his farewell match last Sunday.
West Coast remain a chance to secure just the second wooden spoon in their proud history, sitting in 17th on the ladder above North Melbourne on percentage only.
