The concussion that Minnesota Vikings linebacker Erin Henderson suffered last Sunday against Indianapolis continues to keep him out of practice.

Henderson missed a second straight day of practice and if he's unable to play against the San Francisco 49ers this week, Marvin Mitchell would step in as the starting weakside linebacker.

Other defensive personnel sets would be affected by Henderson's absence, too. Though he was to blame for a touchdown pass to the Colts' Reggie Wayne, Henderson finished with 12 tackles and a sack, including three tackles for a loss.

Henderson has 22 tackles and three sacks in his first two games. He's a fifth-year pro out of Maryland.

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