Ryan Kerrigan sacks Michael Vick in Monday’s season opener. (John McDonnell/The Washington Post)

Linebacker Ryan Kerrigan was being evaluated for a possible concussion, Coach Mike Shanahan said following the Washington Redskins’ season-opening loss Monday night to the Philadelphia Eagles.

The outcome of that evaluation was not immediately known.

It’s not clear if Kerrigan will be available to practice this week or play Sunday at Green Bay. Under NFL guidelines, a player who suffers a concussion must be cleared by an independent neurologist before practicing or playing in a subsequent game.

More on the Redskins:

For Griffin, a frustrating return to action

The Takeway: Defenseless in opener

Boswell: Eagles leave Redskins stunned and confused

Postgame quotes from live blog | Game summary