The 20-year old sustained a fractured foot whilst captain of Scotland's U21s in their 2-0 loss to Spain on Friday and will now undergo surgery which is likely to keep him out until the new year.
"Ryan Jack has this morning been to see a specialist to assess the foot injury he suffered while away with Scotland Under 21s," read the club's official website.
"Following consultation it was confirmed the fracture will require surgical repair. Ryan is expected to be out until the end of January.
"Everyone at the club wishes Ryan a speedy recovery."