Currently a free agent: Dylan Gandy (he was tendered as a restricted free agent before the lockout but will likely be unrestricted under the new CBA)
New to the team: None
The Detroit Lions' center position the last couple of years has been Dominic Raiola and Dylan Gandy. Raiola has been the starter since 2002, and Gandy has served as his backup since 2009.
Gandy is set to become an unrestricted free agent under the new CBA since he has been in the league for five years. The Lions tendered him before the lockout began in case he ended up being a restricted free agent, so they have indicated that they want Gandy back. He is a good player to have as a backup offensive lineman because he can play center or guard, and that versatility means the Lions can use an extra roster spot on a different position.
The other center on the roster for the Lions is Dan Gerberry. He was signed as an undrafted free agent in 2009 and has been with the Lions ever since, spending time on the practice squad for the most part. He will try to compete for a spot on the 53-man roster during training camp and the preseason this year.
Need going forward?
If the Lions can find an undrafted free agent who plays center and can serve as a camp body, I wouldn't be surprised if they sign someone. Like the other positions on offense, that's about as big of a need the Lions have at center.