Shields is a great player. Period.
This half a season BS is just that. BS. In 2011, Shields had 4 INTs, 13 PDs, 1 FF and 38 Tackles, in 15 games played during a season where we nearly went undefeated. Everybody in the world was throwing on our asses...
Forget that we had NO pass rush that year, and might as well forget what that does to a team's secondary (hangs 'em out to dry, maybe?). He greatly improved his tackling last season in run D, not statistically, but it was readily apparent in watching him play. If you didn't see it, then you weren't watching. Sam is a young, quality corner with exceptional experience at the position for his age.
I think one of the bigger problems in ironing out a deal is that Ted has done so well in adding talent at CB over the past 3 years. He has so much leverage that he literally could let him walk without us skipping much of a beat IMO. This is just business, and I think Ted will more than likely lock him up with a huge deal that will keep him in GB for what should be the prime of his career. Whatever those numbers are now, they will seem reasonable 3 years down the line. Ted values quality CBs, but Ted ALWAYS plays to his leverage.
Locking up Shields will insure quality CB play for a good many years, regardless of how Tramon Williams transitions the ending of his own career. I think we just hope for the best here. Either the numbers don't work for Ted and he plays his hand out with Shields, or he pony's up and we are insured of quality play at the position, with a very deep roster of DBs, for at least the next 4 years.