U.S. international Fabian Johnson has suffered a muscle tear in his right calf and is set for several weeks on the sidelines.
It is unclear whether the versatile 27-year-old will return in time for Borussia Monchengladbach's Champions League debut in mid-September.
Johnson went the full 90 minutes in Gladbach's 4-0 defeat at Borussia Dortmund on Saturday, and like his teammate, was far from impressive in left midfield against the Thomas Tuchel XI.
On Sunday, the defender, who started against BVB despite missing the majority of preseason because of the Gold Cup, tore a muscle in his right calf, and is set for several weeks on the sidelines.
"He is out until further notice," the club told ESPN FC, adding that it's down to the healing process whether Johnson will return in time for the club's Champions League debut in mid-September.
Elsewhere, Borussia Monchengladbach are set to sign Nico Schulz from Hertha BSC for a reported transfer fee of €3 million. The 22-year-old has one year left on his contract at Berlin, but has been reluctant to pen a new deal.
Schulz usually plays at left-back, but during preseason also was tested in a more attacking role. He came off the bench for Hertha in the second half of their 1-0 win at Augsburg on Saturday.