The San Francisco 49ers probably are not going to overhaul their defensive scheme to accommodate newly added tackle Glenn Dorsey.

Initial reports suggest Dorsey will help fill the void created by nose tackle Isaac Sopoaga's departure to the Philadelphia Eagles. In that case, Dorsey would also provide insurance at defensive end in the 49ers' 3-4 scheme.

That could be the end of the story. But Dorsey's addition to an evolving line rotation invites a closer look at where the 49ers are headed on defense. It can serve as a launching point for a discussion I've been wanting to have for some time.

First, some background on why I think the 49ers have some decisions to make as they seek to sustain their recent success under coordinator Vic Fangio.

General manager Trent Baalke hinted at the subject when suggesting during the NFL scouting combine that the 49ers used a smaller rotation along their line for philosophical reasons, not depth reasons. In my view, the comments sounded like something a GM would say if he thought the defensive coordinator should be using a larger rotation.

Fangio has been known to favor veteran players. That is typical for coordinators running complex 3-4 schemes. Those schemes often function best with veteran players. Veteran players carry higher price tags. Higher price tags force tough personnel decisions as teams manage salary caps that aren't growing all that much from year to year.

That is where the 49ers are at right now. They knew they would have to let certain defensive veterans leave in free agency. Dashon Goldson was one of them. There has also been talk recently about how a scheme change could help the 49ers take better advantage of cheaper labor.