"As of now, yeah, it looks like I'm going to miss it," Landry said Wednesday.
Landry is uncertain when he will return. His setback was confirmed at a doctor's appointment Tuesday.
"It's a day at a time," he said. "... Hamstrings can be tricky."
Landry made a posting Tuesday on his Twitter account that appeared to blame the Redskins' training staff for his slow recovery.
"Uuhhh oo it ain't my fault," Landry tweeted. "blame the genius circus staff for the rush. wouldve been there 2wks ago. Im sry but saga cont."
Landry later removed the riff, but the The Washington Post already had retweeted it. The four-year veteran distanced himself from the tweet Wednesday.
"Personally I think I pushed it too hard," he said. "It's nothing the training staff did. I take full responsibility."
Landry was one of the Redskins' top defensive players during the 2010 season before an Achilles' tendon injury ended his season early. He completed his recovery from that injury during training camp but then hurt his hamstring warming up before the Aug. 19 preseason game against the Indianapolis Colts. He was removed from the physically unable to perform list Saturday.
Washington's other significant injury concern is tight end Chris Cooley, who missed all of preseason while recovering from knee surgery.
The Associated Press contributed to this report.