MELBOURNE draftee Christian Petracca is determined to remain "upbeat" despite the fact he will have a season-ending knee reconstruction next Tuesday.

The No.2 pick in last year's NAB AFL Draft ruptured the anterior cruciate ligament in his left knee at training on Monday with scans confirming the "devastating" news.

He is set to have a traditional reconstruction.

"It's a little more frustrating if anything. I've never had an injury like this before," the 19-year-old said on Tuesday.

"Mentally, it'll definitely challenge me, but I'm looking forward to [the process of the rehabilitation].

"I'm a pretty upbeat kid, and so long as I can bring that positivity day in day out then the rehab and the year will fly."

A Melbourne spokesman confirmed to AFL.com.au that Petracca was likely to join Jack Trengove on the club’s long-term injury list, with any potential replacement to be determined down the track.

Petracca said the injury was a "blur" and at first he believed he had only hyper-extended his knee, rather than a full-blown ACL.

After pushing off a teammate to create space during a training drill, he felt his knee "click back" before limping off the track to be assessed by the Demons' medical staff.

The midfielder said he had performed that kind of manoeuvre many times during his junior basketball days and it was unfortunate that his knee gave way.

Renowned surgeon Julian Feller will perform the surgery on Petracca's knee and already the teenager is looking forward to approaching his rehab.

Petracca said he would use his year out of the game to improve his football knowledge and brush up on some of the finer points of the game, through watching edits and completing some scouting reports.

Asked whether he was confident he could get back to playing at AFL level after completing his rehab, Petracca was definitive in his response: "I can't really look at the future right now, but so long as I do all my rehab right … I reckon I will."

Petracca was firming for a round-one debut and many experts believed he could have made a significant impact in his first year at Melbourne.