Melbourne midfielder Christian Petracca suffered a significant knock to his ribs early into his side's King's Birthday bout with Collingwood, with the blow eventually forcing the Demons into a sub change.

Petracca was seen in agony on the ground following a marking contest in his side's attacking 50, with replays showing the knee of Collingwod's Darcy Moore driving into Petracca's midriff as he approached the contest from the side.

The Demons star was left holding his side as medical staff rushed to his need, with Petraca slowly getting to his feet and making his way from the field and into the rooms at the opening break.

Petracca didn't return to ground level for the start of the second quarter amid concerns of significant damage to his ribs, with the Demons bull eventually coming back onto the field.

It initially shaped as an early blow for the Demons, with Petracca among his side's top performers in the opening term.

The Norm Smith Medal winner had eight disposals, four marks and over 200 metres gained in the opening term, and would be moved to a more forward role following his return to the game.

The 28-year-old saw the end of the first half but would again start the third term on the interchange in the hand of medical staff, with Melbourne soon announcing Petracca had been subbed out of the match.

Speaking to Channel 7, Demons football boss Alan Richardson provided an update on Petracca, who was yet to be sent to hospital but will require scans.

"He's pretty sore. He'll get scans," Richardson said.

"He's okay, he couldn't get movement."

The Demons brought in veteran Jack Billings as the tactical sub in the early stages of the third term.

Melbourne are scheduled for a Round 14 bye, meaning Petracca will be afforded some time between games if he is still hampered by the ailment in the coming days.

You can follow Collingwood vs Melbourne live via Zero Hanger's match centre below.

Collingwood WON BY 38 POINTS