With Garcon out, first-year pro Aldrick Robinson is expected to take his place. He had four catches for 52 yards last week after Garcon was hurt.
Robinson was a sixth-round draft pick out of Southern Methodist University in 2011 and played on the Redskins' practice squad last season.
"He's got a lot more confidence in his hands," Shanahan said, according to The Washington Post. "Being here at the OTAs and summer camp, he is a lot more comfortable in the system. He made a couple of big plays in preseason where he has a lot of confidence. You can see that. He has a lot of speed to separate from defensive backs throughout the league. Especially when you take a look at the first game and the catches he made, he should have a lot of confidence."