The Redskins have placed three defensive players, including safety LaRon Landry, on the physically unable to perform list.
Safety Kareem Moore and linebacker Robert Henson are also on the PUP list.
Landry is still recovering from an Achilles injury suffered last year. He spent the last seven games on injured reserve.
"We've got him on the PUP as a preventative measure more than anything," Shanahan said of Landry. "He's not at 100 percent, but he looked pretty good [Friday], so hopefully he won't be too long before he's ready to go."
Shanahan said the Redskins are being cautious with injuries because they were unable to monitor rehab programs with players due to the lockout last offseason.
"He's out there watching practice and getting all the mental reps," Shanahan said. "I want to get him ready for the New York Giants [in Week 1]. I'm not really worried about getting him ready for Pittsburgh [the first preseason game]."
Both Moore and Henson are returning from knee injuries suffered last season.
Henson spent the entire season on injured reserve after injuring his knee in preseason. Moore underwent knee surgery in late December and also finished the season on injured reserve.