Raiola was scheduled to count for $6 million dollars against the salary cap in 2013 -- and Raiola could very well have been a cap casualty if his cap number stayed there. Raiola, who has been with the Lions for the duration of his 11-year professional career, agreed to restructured his deal in order to remain with the Lions -- though details of the new deal are currently unknown.
Detroit's offensive line collectively graded out as Pro Football Focus' No. 7 offensive line in 2012, despite Detroit's unsuccessful season.
Detroit has already released Titus Young, Kyle Vanden Bosch and Stephen Peterman to save nearly $9 million dollars of cap space in 2013. It's unknown how much cap space Detroit will save by restructuring Raiola's contract, but the restructuring of the deal will only help Detroit's cap situation as the Lions move forward this offseason.
Sean Yullie wrote about Raiola over at Pride of Detroit, SB Nation's Lions blog, and offers insight as to why the Lions opted not to cut Raiola.
While I personally would have liked to see the Lions finally make an upgrade at center and move on from Raiola, it's clear they didn't want to shake up the offensive line quite that much. Already they are in need of a new right guard, and they could be in need of a new right tackle as well with Gosder Cherilus set to become a free agent. I suppose it's still possible for the Lions to find a new center, but with Raiola restructuring his contract, there's less pressure to fill that particular need.
Raiola, at the least, provides continuity to Detroit's offensive line, which was one of football's best in 2012.