Bear with me here. I know that this may sound like the most ridiculous thought you've ever heard, but there is a slight chance that John Henderson could be cut after training camp. But there is a strong chance that he will be next to Tommy Kelly when the Raiders are at Nashville.
Why A Camp Body? Last year, the Raiders also acquired a veteran right between OTAs and training camp. His name was Lorenzo Neal. He was expected to be an instant starter by many fans, but he was out of a job before the season opener. There was also Jeff Garcia.
Also, the Raiders have two young defensive tackles who could rise up and pass Henderson in training camp. Those young men are second-year player Desmond Bryant and undrafted free agent Kellon Heard.
John is playing on a one-year contract, the length usually given to a player that a team is unsure about for some reason. That reason could be his age and stats. He is 31 and is coming off a 26 tackle season. Not great production for a "run-stuffer."
Why A Starter? Look at his resume. He has been a two time Pro Bowler. Along with that, he has never missed much time for an injury, or anything at all.
With his size (6'7" 335 pounds) he will eat up the blockers and allow his linebackers to make plays near the line instead of the usual four-six yards down the field. His production should be measured by the number of times he is double-teamed.
Along with his age comes the experience. He can be a mentor to the young tackles Bryant and Heard. They would benefit more from having him around all season instead of just training camp.