Commanders backup Marcus Mariota out for rest of preseason with MCL sprain

The Washington Commanders will finish the preseason without their top backup quarterback. Marcus Mariota has been diagnosed with a sprained MCL that is expected to keep him out for the remainder of the exhibition slate, sources told ESPN's Adam Schefter (ESPN).

Mariota went down on Washington's fourth offensive play of Friday's opener against the Miami Dolphins. The injury was noncontact — he collapsed to the turf right after handing off to running back Kaytron Allen — and he was surrounded by trainers before walking off under his own power. He stopped in the blue medical tent, had a brief conversation on the sideline with starter Jayden Daniels and offensive coordinator David Blough, then headed to the locker room.

Whether Mariota is healthy enough to serve as Daniels' backup for the Week 1 opener against the Philadelphia Eagles remains unclear. Sam Hartman and seventh-round rookie Athan Kaliakmanis are the only other quarterbacks on the roster, which means the Commanders could look to add another arm to get through the final weeks of the preseason.