The Raiders designated Mariota (quadriceps) to return to from injured reserve Wednesday, Paul Gutierrez of ESPN.com reports.
As expected, Mariota will return to practice this week, opening a 21-day window for him to be activated from injured reserve. It's unclear if the 27-year-old will be available for Sunday's game at Denver, but once he's deemed ready to go, he should supplant Nathan Peterman as Derek Carr's top backup.