Safety Brandon Meriweather is helped off the field after injuring his knee during the preseason. (John McDonnell/Washington Post)

Safety Brandon Meriweather (knee) and cornerback Cedric Griffin (hamstring) both sat out practice Wednesday, coach Mike Shanahan said. Receiver Aldrick Robinson (concussion), wide receiver/returner Brandon Banks (hip) and running back Evan Royster (knee) were limited. Tackle Trent Williams (knee) practiced fully.

Shanahan said Robinson will be tested for concussion symptoms Thursday before a decision is made on whether to clear him to play. Robinson wore a yellow non-contact jersey Wednesday.

Shanahan said receiver Pierre Garçon did well Sunday, but is still working his way back into “football shape.”

Shanahan said two improvements in this year’s receiving unit are the players’ ability to pick up yards after the catch and block effectively.

He said running back Ryan Grant, who was signed last week, continues to pick up chunks of the playbook, but he isn’t yet sure if the former Packer will play Sunday.