Back ailment lingering for Vikings center Sullivan

EDEN PRAIRIE -- Minnesota Vikings center John Sullivan has been dealing with a back injury for the past week. Coach Mike Zimmer says the team is "just being cautious with him."

Sullivan missed practice again Tuesday. He has been off the field for the last seven days, including the exhibition game Saturday. Joe Berger started instead against Tampa Bay.

Safety Antone Exum returned to practice. He had been out with a hamstring injury, setting him back in the running for a spot on the starting defense.

Zimmer also declared Gerald Hodges the starter at middle linebacker, for now, in the base defense. Rookie Eric Kendricks will replace Hodges and play next to Anthony Barr in the nickel package in passing situations. The Vikings play their fourth preseason game Saturday at Dallas.