Limited commentary with this post, because it’s somewhat self-explanatory.  I decided to go back and calculate an on-going QB Rating for several prominent players to see how each would have looked, statistically, after every appearance made.  Obviously, this relates to Nick Foles.  Basically, I cannot think of a single QB who has had a start to his career anywhere near as good as Foles has (statistically) and then NOT gone on to have a good career.  However, I figured it would be instructive to look at some successful QBs and see how they progressed over time.  Below is the chart.

Before we get there, though, a PSA: The NFL QB Rating calculation, while useful, is very convoluted.  Almost nobody knows it or has even seen it, so for your education, here it is (from Wikipedia):

Fun stuff, eh?

Anyway, back to the subject.  Here’s the graph, I suggest you click to enlarge:

I only included the first 100 appearances (NOT starts) for each player.  Note that this is an ongoing calculation, so it becomes less susceptible to change with every appearance.  I’m hesitant to draw any conclusions from such a small sample size, but including other QBs (I originally included Vick, Brady, Brees, and Josh Freeman) makes the graph too hard to read.

In any case, I’m going to build the sample from here to see if we can divine a good idea of when, regarding Foles, we can exhale.  For now, just take note of how “poorly” each of the included QBs played to start their careers.  And because you knew I would, I included Foles below, along with Brady and Brees.  Notice that none of these guys had as high a QB rating after 14 appearances as Foles does.  Moreover, among these guys, Foles tracks most closely with…Tom Brady.   I know attempts would be a more helpful measure, but I don’t have data for that, so…this:

Update: Should have noted this originally, but the chart doesn’t account for the general offensive inflation the league has seen since guys like Peyton started their careers. Regardless, the adjustment would only involve shifting Foles’ line down slightly, and would’t significantly change how things look.  The trend, obviously, would remain the same.