Ertz specifically suffered a high ankle sprain, added ESPN's Adam Schefter.
In a further blow to an already injury-ravaged Eagles offense, running back Miles Sanders will reportedly miss Thursday's game against the New York Giants and potentially the week after due to a knee issue.
Philadelphia has yet to field a full-strength offense this season. Alshon Jeffery hasn't played, DeSean Jackson has been out since Week 3, and the team's offensive line has been hit with multiple season-ending injuries to key starters.
The Eagles are 1-4-1 through six weeks. Carson Wentz is struggling immensely amid the injuries to his supporting cast, completing 58.7% of his pass attempts and throwing eight touchdowns against nine interceptions.
Ertz has recorded 19 catches for 139 yards and a touchdown, far below his usual production. Meanwhile, Sanders has logged 434 rushing yards and three touchdowns.