The Redskins’ sigh of relief was quickly replaced by a shrieking scream.

Hours after it was reported second-round pick Derrius Guice was believed to have suffered only a minor knee injury, an MRI exam revealed he actually tore his ACL, the team announced. The diagnosis ends his rookie season almost immediately after it had begun. Tight end Manasseh Garner also suffered a torn ACL.

Guice left at the end of the first quarter of Washington’s preseason opener Thursday night against the Patriots after he was tackled following a 34-yard gain that was negated by a penalty.

The former LSU star was fourth on the Redskins’ depth chart at running back, but was expected to have a significant role this season.