Xhaka limped off the park in Switzerland's European Championship qualifying win over Estonia on Monday and has since been diagnosed with a tear in the collateral ligament of his right ankle.
Most worrying for the club's fans is the announcement on Gladbach's official website did not mention a potential return date, suggesting the midfielder faces a long spell on the sidelines.
Shulz also faces months out after rupturing a cruciate ligament in his left knee after going down in a tackle by an opposition defender in the club's friendly fixture against Duisburg on Friday night.
"Nico will have an operation in the coming days, and will then need roughly six months to recover," Dr Stefan Hertl told the club's website.
After a disappointing start to the season, in which Gladbach lost all five of their opening league fixtures, they have recovered well to win their last three games on the trot and head coach Lucien Favre will hope these injuries do not halt their momentum.