Mertz suffered a knee injury in Thursday's preseason opener against the Chargers, Aaron Wilson of KPRC 2 Houston reports.
Mertz limped to the locker room at halftime and will undergo further testing to determine the severity of the injury after coach DeMeco Ryans hinted after the exhibition that it could be an ACL issue. Mertz completed four of seven passes for 23 scoreless yards prior to his departure Thursday. He also rushed three times for 15 yards.