MELBOURNE's ruck stocks have taken another hit with Jake Spencer to miss the next six to seven weeks with an AC joint injury.

Spencer was one of three Demons that suffered injuries in the club's 13-point loss to Richmond during Monday night's Anzac Day eve clash.

Melbourne midfielder Christian Petracca received a knock to his knee, but has been cleared of any major damage and will be monitored throughout the week.

Meantime rookie forward Tim Smith will remain in hospital after sustaining a punctured lung and a broken rib in the first half.

It is unclear how long he will be sidelined for.

The extent of Spencer's injury was revealed on Tuesday after the big man had scans.

“Jake received a knock to his AC joint early in the game last night and was ruled out prior to half-time," Melbourne football manager Josh Mahoney told melbournefc.com.au.

"He had scans today (Tuesday), which showed damage to the AC joint. He will consult a surgeon tomorrow, with the most likely option being surgery later in the week."

With No.1 ruckman Max Gawn sidelined with a long-term hamstring injury, it leaves coach Simon Goodwin with a dilemma.

Developing big man Mitch King returned from a knee reconstruction on the weekend to play his first VFL game since last season.

Goodwin said after the loss the lack of available ruckmen may force the Dees to think outside the square.

"As a coaching group we've always said that we want to be adventurous and we might just have to be that now," the coach said on Monday night.

"We've lost a few soldiers in Max and Jake, potentially, so we'll have to think a little bit laterally and come up with a plan this week that's going to work for the footy club." 

Jack Watts was forced into the ruck after Spencer went down, while former Kangaroo Cam Pederson could be another pinch-hitting option given his strong recent VFL form.

Melbourne plays Essendon on Sunday at Etihad Stadium.