Melbourne defender Marty Hore has suffered a major knee injury, rupturing his left anterior cruciate ligament on Friday morning. 

The 24-year-old went down in an innocuous tackle towards the end of a gruelling three-hour training session at Casey Fields.

“Unfortunately, the scans have confirmed that Marty has ruptured his ACL and will miss an extended period of time,” General Manager, Football Performance Alan Richardson told Melbourne Media.

“This is devastating news for Marty and the club, as he was preparing for the season ahead.”

In what will be a challenging time, Richardson said Hore will receive plenty of support throughout the recovery process.

“Marty is a very impressive and resilient person, and we will fully support him through his rehab,” he said.

"He'll meet with the surgeon next week to discuss the appropriate treatment required to repair the ACL."

The intercept defender, who has played 14 career matches, was a mature aged recruit for the Demons, being selected with pick No.56 in the 2018 National Draft.