He is judged by others on the team who don't play the stuff he needs to do and does IMO at an above level.....No he isn't Pro Bowl, but the things he does are just as important as what a Pro Bowl player does (and Saffold was never a PB'er...but I can agree he played at that level) Then again I can remember how some said he was a jag and was glad when the raiders made the play on him, but failed....
IMO there are less D Line chosen than there are O lineman to start with for that accolade (Pro Bowl).
The guy plays and moves around as he is asked to do through several DC's as long as he's been around. I realize your point of money being tight going forward....but to me you may get a guy cheaper in the draft to replace him and save money, but at the same time you are missing out on a ton of experience in different D's who are proven at the Pro level.
Bring out your scale and weigh in....experience and some money or less money and a learning curve....He leaves and someone is going to get a guy who has 4 years or more..(injury not counting) left of above average ball....in certain areas I see easier replacement but on a D Line not so much.....IMO he's worth the re-up......