Derek McInnes has revealed his fear that Zak Vyner could miss the rest of the season through injury.

The defender had to be substituted in the first half of Aberdeen's 1-1 draw with Hearts at Tynecastle, having injured his shoulder.

Dons boss McInnes is concerned the recurrence of a previous problem could need surgery.

"There's a concern there," he said. "Last time (he was injured) he was out for three weeks," he said.

"The specialist said he didn't need an operation. There will be a revisit to the specialist and between ourselves and Bristol City we'll make the decision that is best for Zak.

"I think there's a real risk that he might need the operation that was suggested prior, which would mean he would be out for the season."

Should the on-loan Bristol City defender find himself sidelined long-term, McInnes said that he would be likely to find a replacement when the January transfer window opens.

"We're already without Greg Leigh for two months, Craig Bryson goes in for his operation in the next couple of days," he added.

"If that (surgery) is the case we can do smart work in January and bring two or three additions in."