A gallant Sydney have overcome key injuries to down Melbourne by nine points at the MCG and leave the Demons in grave danger of missing the AFL finals.
Reduced to two men on the bench after Sunday's first quarter, the Swans showed tremendous resilience to regroup and hold off a late Melbourne surge for a 13.9 (87) to 10.18 (78) victory.
The Demons trailed by 28 points at three-quarter time but got within seven points when skipper Nathan Jones kicked truly with five minutes on the clock.
Jones had another shot on goal minutes later but sprayed it wide and the Swans prevailed in front of a 51,424-crowd.
"Our boys were just terrific," Sydney coach John Longmire said.
"When you have two players down at quarter-time and you're playing against a team on their home deck who have had a fantastic year ... it's just a fantastic win."
The loss is a potentially lethal blow for the Demons, who slip to seventh on the ladder and come up against West Coast (away) and GWS in their two remaining games.
Questions will continue to be asked about the resilience of a side that remains winless against top-eight rivals.
"It's incredibly disappointing," coach Simon Goodwin said.
"It's been a tale of some of our games this year where we've just struggled to connect and have efficiency inside forward-50 ... we certainly didn't do that very well."
Sydney climb to sixth but were dealt a major blow with luckless backman Alex Johnson suffering a suspected torn ACL and Nick Smith injuring his hamstring.
Johnson limped from the ground in the arms of the trainers after his "good" right knee buckled underneath him while pursuing Jesse Hogan in the forward pocket.
The 26-year-old's comeback last week was his first game since the 2012 grand final, having undergone 12 knee operations - including five reconstructions - in the 2136 days between.
Melbourne also had injury concerns with Hogan sitting out most of the third quarter with a foot issue and Jayden Hunt hobbled by an ankle injury.
Ruckman Max Gawn had his corked right calf strapped after failing to train earlier in the week and was well down on his usual impact around the ground.
Sydney trailed early but piled on six straight goals during a dominant second term to snatch a 14-point lead at the major break.
Melbourne led the inside-50 count but were killed by inaccuracy in front of goal with a halftime scoreline of 3.12 compared to Sydney's 7.2.
The Swans dominated clearances and contested possessions in the third term to open up their lead at the final break before withstanding a late Demons comeback.
Best-afield Isaac Heeney (19 disposals, two goals) stood tall with several clutch marks in critical moments, including a high-flying mark of the year contender over Hogan.
Lance Franklin booted two majors in an intriguing battle with Sam Frost while skipper Josh Kennedy and Jake Lloyd were also influential.