Xhaka is regarded as one of his nation's key men but it appears that his involvement in Russia next month is now uncertain.
According to RTS, Xhaka needed to be helped off the training pitch and taken to hospital after sustaining an injury to his left knee.
An update is yet to be provided by the team's medical staff but Switzerland's opener with Brazil is just over two weeks away.
Switzerland will first take on Spain and Japan in warm-up matches but as it stands, it is unlikely that Xhaka will play a part in those games.
Xhaka has scored nine goals from 61 appearances for his country.