Jordan Reed will be absent for the Monday Night Football match with the San Francisco 49ers.
The Washington Redskins rookie suffered a knock to the head during last weekend's defeat to the Philadelphia Eagles and has not participated in practice since.
ESPN insider Adam Schefter tweeted: "Due to a concussion, Redskins TE Jordan Reed will not play Monday night against San Francisco."
The injury is a big loss to the Redskins, with the tight end having caught 45 passes for 499-yards this season so far, scoring three touchdowns in the process.
Once Reed completes a week of rest, he will be eligible to practice again having followed NFL concussion protocol.
The Redskins lie at the bottom of the NFC East with a 3-7 record.
