The Dundee captain will be sidelined for three weeks after his knee injury has turned out to be worse than first feared.
“Darren is probably looking at three weeks now, going by the scan." McCann told the media.
“He has been properly assessed and it is a bit of a blow.
“It’s his knee. He took a knock on it against Hamilton and we’ve got the scan back.
“It suggested it was a wee injury to one of his ligaments so we had to make sure and that is the case.”
With O'Dea ruled out, it will more than likely mean that the young paring of Kerr Waddell and Jack Hendry will face Aberdeen at the centre of defence.
Randy Wolters also looks set to miss tomorrows game but Roarie Deacon has just returned to training so may feature at some point.