Carl Starfelt has revealed he's sweating on the results of an X-ray to find out the extent of the injury he picked up playing for Sweden.
The Celtic defender had to be stretchered off during his country's Nations League win in Slovenia just before half time as the 27-year-old won his fifth cap for Sweden.
Starfelt will get checked out in the coming days, but was pessimistic after the game. He said: "I felt a stabbing pain in my back so I had to go off.
"Of course it's not fun, especially not when you get the chance to play and you want to take your opportunity.
"But sometimes it's like that in football, I have to see now what kind of injury it is.
"We'll see what it is, but it does not look very bright. If I am lucky, the X-ray may not show anything and I can recover in a few days, but right now I do not see it as very likely."
It was Celtic stopper Starfelt's first competitive start for his country and, with his team leading 1-0, came as a blow just before the interval as AIK's Alexander Milosevic replaced him.
He now faces a potential long-term absence in a blow to Ange Postecoglou 's defensive options.
Sweden boss Janne Andersson said afterwards: "It is a problematic situation. He is a very important part of the team.
"Even he does not have experience, you want a centre back you are used to."