The pragmatic litmus test would be the market speaking:
At this point in time, I cannot think of:
1) a single team, including the jest who, if had the choice, would take Sanchez over Eli
2) No more than 6 or 7 teams at most who wouldn't trade their healthy starting QB for Eli vs.
no more than 7 or 8 teams (generously speaking) who would trade their starting QB for Sanchez
3) The likelihood that if respectively put up for trade, Eli would fetch a package including at least 2 firsts and a couple of seconds, while Sanchez would likely command a late second or early 3rd rounder in exchange.
These are the high water marks that an egalitarian unsentimental, pragmatic marketplace would realistically place on these 2 . Unless your world is viewed through green-colored vacuum-visioned lenses, you're gonna acknowledge the real world veracity of this assessment. One can argue over minutiae and ref calls to they're blue in the face: regardless, the market knows what it knows and presently doesn't consider Sanchez a valid starting QB with untoward upside.