Stafford has not diminished an iota since he was a rookie.
His arm strength is still second maybe only to someone like Josh Allen.
His legs are good.
He's not a concussion machine.
The Rams are smart with him and when he's hurt, he's rested.
There is no more QB friendly coach than McVay.
As long as Stafford has a fire in the belly to play, and he stays reasonably healthy, he'll be around a few more years.
A QBs life span has greatly increased, and it is all the greater for pocket passers.
Besides, this assumption that if one picks high enough in the 1st round you'll get a top notch starting QB is not supported by history. Getting a good QB out of the draft seems to be mostly luck. So, if I'm the Rams, I take my best shot every year in the 2nd to 4th rounds until I (hopefully) hit on one. And, even better, if a younger and really accomplished QB comes available in the FA market (rare) then they need to see what they can do to acquire him.
The Rams need to stick with Stafford as long as he sticks with them. What they need is to realize that injuries do and will happen to him, and they need to invest in a good back up that can win a couple of games for you. Wentz is not a bad choice, and it remains to be seen how that works out in the longer run. If that is even the intention for either party.
