The Dons are waiting anxiously for news on just how long the centre-back will be ruled out for after he was replaced with 20 minutes left of their 1-1 Europa League draw with Macedonian side KF Shkendija in Skopje.
Midfielder Jack told RedTV: "We are all gutted for Mark because he's a big player for us. He played a lot of games for us last season and is very strong for us at the back.
"We're just hoping it won't be too bad."
Niall McGinn fired in a precious away goal for the Dons 12 minutes from the end of the first qualifying round first leg.
But Shkendija ensured they are still in with a chance ahead of next Thursday's Granite City return leg when Hristijan Kirovski headed home with five minutes left.
New Dons captain Jack admitted he and his team-mates were left deflated by that late lapse in concentration, but he believes Derek McInnes' team are still favourites to progress to face Croatians HNK Rijeka in the next round.
Jack said: "I thought it was a really tough game in tough conditions but we gave a good performance and have given ourselves something to take back to Pittodrie. Hopefully we can get a result.
"The manager sent us out saying that he wanted us to win the match, so to only get a draw left us a wee bit disappointed after, especially as we conceded so late.
"But on the whole we are happy with the performance and the result is still in our own hands.
"We were all disappointed after the game to have conceded the way we did but it was a hell of a header. "