MELBOURNE defender Marty Hore's worst fears have been realised, with scans confirming he suffered a ruptured ACL at training on Friday morning. 

Hore was floored after a crunching tackle deep in defence at Casey Fields and was helped off the oval with the assistance of trainers. 

After being sent for further assessment, the 24-year-old, who failed to play a game last year due to quad and toe injuries, was informed on Friday afternoon he would also miss the entire 2021 campaign. 

"Unfortunately, the scans have confirmed that Marty has ruptured his ACL and will miss an extended period of time," Demons head of football performance Alan Richardson told the club's website. 

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

Reigning best and fairest Christian Petracca also looked in discomfort early in the two-and-a-half-hour session after copping a heavy knock to his left shoulder.

While he was taken from the field for assessment, the midfield gun returned moments later with the shoulder strapped and finished the hit-out unencumbered.

Forward recruit Ben Brown impressed during one hour of match simulation, booting three goals with his typical long run-up and dead-eye approach on goal.

The 28-year-old later jarred his finger but was able to join teammates for running efforts that closed out the morning.

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Brown combined in the forward 50 with Sam Weideman, while a lively Bayley Fritsch alternated between attack and the wing with a leaner Tom McDonald. 

Steven May sat out the match play due to a minor ankle injury but will return next week and was among a group of six who were put through lighter drills on the secondary oval.

He was joined by Clayton Oliver, who was managed for loads, Joel Smith, Kysaiah Pickett, Angus Brayshaw and Aaron vandenBerg, who is easing back after being forced to quarantine following a stint in NSW over his break.

Brayshaw continued to step up his running as he works back from a foot injury that cut short his 2020 campaign and required surgery.

Second-year tall Luke Jackson was reduced to running laps after reporting recent Achilles awareness and will be back in full training next week alongside draftee Jake Bowey, who nursed a corked calf.

Veteran Michael Hibberd was restricted to watching on and assisting coaches, still recovering from an ankle injury, while Harrison Petty (groin) missed.

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In defence, Jake Lever excelled alongside Adam Tomlinson and Jay Lockhart who played a lockdown role in the stronger 'A' side.

Jayden Hunt played off half-back in the same line-up and will settle in defence this season after several years playing as a half-forward.

Captain Max Gawn showed no signs of the knee injury that hampered parts of his 2020, covering the ground with ease for the entire session.

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Jack Viney impressed in the midfield and landed a heavy blow on Weideman that left the forward rattled, while first-round pick Bailey Laurie was clean in congestion.

Kobe Farmer, the son of Demons great Jeff, booted one goal and showed promising signs as he vies for one of two vacant rookie spots ahead of the season.