Reed (concussion), Allen (knee) out for Redskins

ASHBURN, Va. -- The Redskins will once again be without key players for a game. Tight end Jordan Reed was ruled out of Sunday's game versus the Dallas Cowboys with his concussion. Defensive end Jonathan Allen also was ruled out after suffering a Grade 1 knee sprain in the season opener.

Reed had increased his practice reps throughout the week, fueling optimism that he would return from the concussion he had suffered in the third preseason game. But he was not at practice Friday.

The Redskins currently have only two tight ends on the roster, but could end up promoting Donald Parham off the practice squad if they want to have three active. Not having Reed for a second game hurts their offense, though quarterback Case Keenum did throw for 257 yards in the first half versus Philadelphia in the opener.

Without Reed, the Redskins will have to rely once more on their young receivers. Rookie Terry McLaurin caught five passes for 125 yards in the opener, including a 69-yard touchdown pass. His speed created plays down the field for Washington. It's why the Redskins remain confident in their passing attack.

Meanwhile, Allen sprained his left knee in the first half against the Eagles and did not return. The Redskins loved their line depth entering the season and it's now being tested. Backup Caleb Brantley, considered their fifth lineman, was placed on injured reserve. He suffered a Lisfranc injury in training camp and returned, but he reinjured it.

Additionally, running back Derrius Guice was placed on injured reserve, two days after he underwent surgery to repair the torn meniscus in his right knee. Guice hurt his knee in the season opener against Philadelphia. He would be eligible to come off the list after eight weeks.

With Brantley and Guice both headed to IR, the Redskins have placed a combined 52 players on injured reserve the past two years.

Washington is without two starting cornerbacks as both Fabian Moreau (ankle) and Quinton Dunbar (knee) were listed as inactive. In response, the team signed free agent Aaron Colvin.

Colvin was released by the Houston Texans on Wednesday. In two seasons (11 games) with the Texans, Colvin had 34 tackles, two fumble recoveries and one pass defended.

Information from ESPN's Sarah Barshop was used in this report.