Melbourne star defender Jake Lever has likely ruptured an anterior cruciate ligament in their 49-point AFL win over the Western Bulldogs.
The 22-year-old took no further part in the 15.10 (100) to 7.9 (51) win at Etihad Stadium after he twisted his left knee in Saturday afternoon's first quarter.
Lever was sent for scans on the knee - the same one he had reconstructed as a junior.
"It's a suspected ACL ... it's really disappointing for Jake and the club," coach Simon Goodwin told reporters after the match.
"He's someone we care about deeply, he's really fitted into our group really well.
"He's a very resilient young man. I think we need to get all the information first and go through that process, but lots of guys have come back from ACLs really strongly."
The likely loss of Lever for the season is a huge blow for the Demons, who consolidated their spot in the top four with their sixth win in a row.
Angus Brayshaw and Clayton Oliver set new career-highs with 39 and 37 possessions respectively, Max Gawn had 57 hitouts and Jesse Hogan kicked five goals.
Lachie Hunter (32) and Jack Macrae (31) had plenty of ball, but it was another maddeningly inconsistent performance from the Bulldogs.
The Demons had won 18 quarters in a row going into the clash, but the Dogs ended that streak with a bright start.
The appetite for contested ball that has been sporadic this season was on show, as the Bulldogs booted the first three goals of the game.
But as has been the case too often this year, Luke Beveridge's men went missing.
Melbourne weren't in the same formidable form as they displayed in a 91-point drubbing of Adelaide last week, but their eighth win of the season looked in the bag from a long way out.
Goodwin has tried to play down the hype around his team as the wins have come.
But after they made it six wins in a row for the first time since 2006, expectations of his team will continue to grow.
"Obviously we want expectation and we know that our supporters are really excited by how the team is performing ... we can understand that," the coach said.
"There's a lot of noise and people only comment on what they see, but it's really important for our group ... to understand that that noise is just fake.
"All we need to focus on is what we see right in front of us - that next contest, that next quarter, that next game.
"If we can continue to do that ... we'll continue to see results like today."