I think that's an interesting question. If Capers gets fired and they hire someone outside the current staff, it could be way over 7 (counting starters gone too). If they promote someone on the staff to DC, I'd guess there'd be less turnover.
With regard to starters are you talking about all starters? For example what if they offer to Raji $8M/year (gag) but another team pays him more? That's a starter gone but not because they "fired" him. Same thing if Finley's injury is career-ending.
Good question. The short answer, from my perspective, is that not getting Raji signed is a "firing".
We'll probably never know, but if the $8 million/year offer was light on the signing bonus and guarantees, it was a contract offer intended not to be accepted or, at best, a "re-prove yourself" offer with an easy out in 2015 if he didn't step up his game. That's the kind of deal Finley signed. If that same type of deal was offered to Raji, the expectation should have been he'd not likely sign it.
One also wonders if the alleged $10 mil/year offered to Jennings before his 2012 injury, which he turned down, was also designed to not be accepted. We'll probably never know about that one either.
One thing you can be sure of...when players with those resumes, at those positions, offered those $ are not happy, you can bet they don't like the bonus/guarantee components.
As for Finley, unlike Collins he immediately stated his intent to play again and so far has stuck to it. If that's his stance come FA time and we don't sign him, I'd consider that a firing. The parallel situation, on a much grander scale, was the Colts deciding not to sign Peyton Manning. I think we can agree that the Colts fired Manning.