The Detroit Lions have in fact brought back offensive lineman Darren Keyton. He was released following the regular season, and he was stuck on the waiver wire until last week. At that point, with the playoffs over, Keyton officially cleared waivers, and the Lions decided to re-sign him on Friday.
Keyton was only released in the first place because the Lions needed a spot after Dominic Raiola's suspension ended. Raiola's suspension resulted in Keyton being promoted from the practice squad to the active roster, but that was a one-game thing.
Had Keyton simply finished the season on the practice squad, he likely would have been signed to a futures deal. Instead, though, with Keyton being stuck on waivers for more than a month, he had to wait for the end of the playoffs to become a free agent. With that finally happening last week, the Lions were able to re-sign him.
Keyton can play offensive guard, but center is his main position. With him back on the roster, the Lions now have four centers under contract for next season. Travis Swanson is set to become the starter with Dominic Raiola not returning, leaving Keyton to battle Taylor Boggs and Braxston Cave for the backup job.