Continued: Henderson's season-ending surgery depletes defense

NEW ORLEANS - E.J. Henderson was determined to emerge as a Pro Bowl middle linebacker this season. Instead, his season ended after four games.

The Vikings placed Henderson on injured reserve Monday. The team said Henderson had surgery on his left foot at the Institute for Foot and Ankle Reconstruction at Mercy Medical Center in Baltimore.

"Our first and foremost concern is E.J.'s long-term health and making sure that his foot is able to properly heal without compromising the results with an earlier return or without the surgery," Vikings coach Brad Childress said in a statement. "He will focus on his rehabilitation to ensure that is the case. Knowing the leader that E.J. is on and off the field, he will remain an active member of this team throughout the year and look to contribute any way he can."

The Vikings did not disclose the exact nature of Henderson's injury. He initially was diagnosed with two dislocated toes, which happened while making a tackle against Tennessee last week. Henderson's foot had so much swelling early last week that the team's medical staff could not get a full evaluation of the injury.

Losing Henderson is a major blow to a defense that entered Monday's game ranked sixth in the NFL in total defense. Henderson was chosen as captain of the defense and was its leading tackler through four games. He had 36 tackles, one sack, three tackles for loss, three quarterback hurries and two passes broken up.

Second-year player David Herron started in place of Henderson against the Saints on Monday. Herron also started against Tennessee after Henderson was benched for one series for being late to a team meeting.

Vikings coaches and players expressed confidence in Herron, but the team also might look at other options, including possibly moving outside linebacker Ben Leber to the middle.

The team also worked out Dontarrious Thomas last week. Thomas played for the Vikings from 2004 to '07 before signing a free-agent deal with the San Francisco 49ers. The 49ers released Thomas before the season and he has not landed another job.

Depth is becoming an issue at linebacker. The Vikings have now lost two linebackers to season-ending injuries. Heath Farwell suffered a torn anterior cruciate ligament in a preseason game.

Henderson's loss hits especially hard. Not only an emerging star, he has blossomed into a quiet but respected leader on the field and in the locker room. He was chosen as a Pro Bowl alternate last season after setting career highs in tackles (155) and sacks (4.5).

In an interview with the Star Tribune two weeks ago, Henderson said he was motivated this season to not only earn a Pro Bowl invitation but also to become the best middle linebacker in the NFL.

"You always want to come out and show that you're the best at this position, the best at what you do," he said. "That's what winners do."

By placing Henderson on injured reserve, the team did not need to make a roster move to clear room for left tackle Bryant McKinnie, who played his first game Monday after serving a four-game suspension for violating the NFL's personal conduct policy. The Vikings had received a one-week roster exemption for McKinnie.