"There's a concern there. 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."

If surgery was needed, McInnes revealed that the Dons would be prepared to recruit in January.

"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."

His counterpart Daniel Stendel picked up his first point in charge of Hearts, after Ryotaro Meshino opened the scoring at Tynecastle.

It could have been more had Sean Clare not seen red for hauling back Bruce Anderson, with McGinn scoring the resulting free-kick.

It stopped the rut of five consecutive defeats for Hearts and Stendel was pleased to see his four changes from a Boxing Day defeat to Hibernian add "power" to his side.

"I can feel we have so much more power in our team. We changed some positions today with Clevid (Dikamona) and (Euan) Henderson and they used the chance," he said.

"We deserved to win; I think. I said to the players before we started the game that I had a really good feeling today.

"The atmosphere in the stadium was important for me. It was a good sign. When I can feel the power from the fans, I think it was a good decision to come to Hearts."