Injury experts believe he is at risk of missing the tournament after withdrawing from the Scotland squad during the international break.
Although there is no clear information about the nature of the defeat and its severity, it is likely that he will not even be fit to play the next match.
Discussing his situation exclusively with Ibrox News, Brar, a physiotherapist and sports scientist, said:
“There is not much information about it, so it is difficult to read about it.
“It’s never a good sign when you have a history of serious injuries but you don’t know what’s going on.
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“This will certainly be a major cause of concern for Rangers and I think he will miss their next game.”
Jack didn’t even feature in the 3-0 win over St Mirren before the international break and it didn’t happen. Good news for the club.
They’ve got an interim manager in charge and a long injury list that got even longer when the 31-year-old’s name was added.
The international break featured a number of important matches for Scotland, but Jack’s physical condition forced him to withdraw from Steve Clarke’s squad.
It remains to be seen what the club’s official word will be when Philippe Clément addresses the media.