Vikings simply can't replace E.J. Henderson
In my book, Henderson ranks with tailback Adrian Peterson and cornerback Antoine Winfield as the three most difficult players to replace on the Vikings' roster. Henderson doesn't have the kind of national profile Peterson and Winfield have, but he's every bit as important to the team. The season-ending nature of his left foot injury is one of the most devastating bits of roster news the Vikings could have suffered.
Those who have watched Henderson's six-year career have seen him develop, step-by-step, into one of the better middle linebackers in the NFC. He has great instincts, trusts them to get a head start on chasing the ball and has improved enough as a pass defender to be included in the Vikings' nickel defense.
An introvert by nature, Henderson also has worked hard to develop enough authority to be a defensive captain and call all of the Vikings' defensive signals. The Vikings really don't have a natural replacement for him and will split his duties among as many as three different players: Second-year player David Herron will get the majority of snaps at middle linebacker, but veteran Ben Leber -- who plays on the strong side -- will call the signals and there might be some changes in nickel situations as well.
This arrangement will help the Vikings piece together Henderson's duties, but there is simply no way they'll replace him. Their defense will be less effective without him.