The Raiders placed Mariota (undisclosed) on injured reserve Monday, Vincent Bonsignore of the Las Vegas Review-Journal reports.
The nature of Mariota's injury isn't known, but the issue isn't related to the shoulder and ankle concerns he dealt with during the offseason, according to coach Jon Gruden. With Mariota out for at least the first three games of the season, Nathan Peterman will serve as Derek Carr's backup.