Jobe Watson could miss the rest of this season, leaving Essendon's hopes of winning back the finals spot taken from it last year in tatters.
The Bombers confirmed on Monday that their inspirational skipper would require surgery this week to fix a torn tendon in his hip.
The recovery process will keep Watson on the sidelines for at least eight weeks, and more likely 10, which means if the Bombers don't reach the finals, his season is effectively over.
There was optimism that the Brownlow medallist had sustained a normal quadricep injury that would keep him out for only three weeks, however club doctor Bruce Reid said the damage was far more serious.
"Jobe has suffered a tear to the rectus femoris tendon right where it is attached to the hip bone, which is a very uncommon injury," Reid said. "The sooner you can sew the two ends back together, the better the healing will be, so he will go in for surgery in the next few days.
"We will not rush him through the recovery process, it is important that we do what is right for Jobe both in the short and long term."
Watson left the ground late in Saturday night's win over Greater Western Sydney, one that put the Bombers just one game out of the top eight.
However Mark Thompson's team now faces the massive task of winning enough games in the second half of the season without its best player and up against a tough schedule with more fallout from the ASADA investigation looming.
The Bombers have to play finals-bound teams Geelong, Port Adelaide (away), Collingwood, Sydney (away) and Gold Coast (home).
Watson said he was disappointed he couldn't lead the Bomber charge to September, although he was hopeful of returning before season's end - with the round 20 match against Richmond the best-case scenario.
"I think the time frame is a bit irrelevant because I just want to make sure the injury heals properly and make sure it is right," Watson said. ''But it would be great to come back, and if the team is playing finals then it would be wonderful to be part of it.''
Sydney, meanwhile, will receive an update on the other big injury out of the weekend's matches - the knee issue that forced Kurt Tippett to be substituted out of Sunday's win over Gold Coast.
Tippett will have scans on Tuesday to determine the seriousness of the left knee injury, but even if he is cleared of any structural damage as expected, he faces a race against the clock to be available for Saturday's blockbuster against Port Adelaide, given the Swans' six-day break between games.
The club is unlikely to take any risks, despite the high stakes in the top-of-the-table clash, and the good news for Sydney is that this latest injury is not to Tippett's troublesome right knee.
Tippett's absence would force coach John Longmire to reshuffle a forward line that has been lethal in the past month, and could provide an opening for Mike Pyke to return and play as a ruck-forward.
The premiership big man has missed the past four weeks with a hamstring injury but got through his comeback in the reserves on Sunday unscathed.
Another key selection decision this week surrounds the return of luckless Fremantle midfielder Anthony Morabito.
The knee injury Michael Johnson suffered against Adelaide is set to sideline him for up to four weeks, but opens the door for Morabito to make a return against Richmond. Morabito, who hasn't played for the Dockers since a standout rookie campaign in 2010 due to three knee reconstructions, displayed strong form in the WAFL at the weekend..