McMaster was hurt during Hume's thrilling inter-league victory over Farrer at Osborne last weekend and will see a doctor in coming days.

"He's had an X-ray and it looks like there is a small fracture in his shoulder blade," coach Matt Rava said.

"Until he sees a doctor we don't know the extend of it.

"It could be a couple of weeks or it could be eight.

"We're keeping our fingers crossed."

The injury is another setback for Osborne who lost defender Andrew Clarke with a ruptured hamstring earlier in the season.

"He's going to be out for a while, it could be 12 weeks," Rava said.

"It's disappointing because he did a lot of work to get back from his knee injury.

"The positive is it will give another young player a chance."

Osborne host big improver Lockhart at Osborne on Saturday.