Melbourne coach Steven King says he still doesn't have any answers regarding Harrison Petty's concussion on the weekend.
Petty's worrying health episode during Sunday's win over Brisbane prompted the club to do a full-scale review of the game to identify what caused him to become unsteady before being assisted from the field.
"It's a unique situation. We're still doing some tests with him," King said.
"We're still not really sure exactly what's happened – we're exploring all those possibilities.
"Because of his history, we've put him in (concussion) protocols at the moment, because that's the most obvious, but we're still not 100 percent sure that's the case.
"There's still a range of things it could be."
Petty has entered concussion protocols, opening the door for at least one change to the Demons side who will go in as favourites against Richmond in the Anzac Day eve clash on Friday.
Veteran Tom McDonald performed strongly in the VFL last week, and poses as a like-for-like replacement.
Speedy defender Changkuoth Jiath will need to get through the week's training sessions as he recovers from a calf injury.
Draftee Tom Matthews has been "unbelievable to date," and has placed himself in the mix for an AFL debut.
The small forward was drafted with Pick 30 last year, but faced an interrupted pre-season due to a complicated knee injury. His latest performance (12 touches, five tackles and a goal) in the VFL was the best for the club.
"Tommy has come off a pretty interrupted year in his draft year, so we're building him back to the level where he'll be able to, not only compete, but thrive," King said.
"Whether that's this week or in the future, he's up there, he's been really consistent with his role."
