To start with, Foles is attempting about 50% more long passes than he did with Andy Reid at the helm. That's a big jump. His current rate of 16.1% is near the top of the league, after placing in the bottom half last season. This change is entirely about the offense; Michael Vick has also seen a spike in his deep balls, bringing him back to 2010 levels after declines the last two years.
But where things start to get crazy is the long ball effectiveness. Foles completed only 36% of passes 20 yards or longer in 2012. That's up to nearly 53% so far this year. Long ball completion percentage is a huge indicator of success. Look at the list of QBs who posted 48% or above last year: Kaepernick, Rodgers, P. Manning, Newton, Griffin, Brees, Wilson. That's elite territory.
Can Foles keep that completion rate up? Unclear. While there may be some regression to the mean, I'm actually bullish on this front. Kelly's offense seems to be giving his QBs a boost. Vick has also seen a double-digit jump in 20+ yard completion rate, so Foles' numbers may not be an aberration.
Touchdown and interception rates are another matter. Foles is averaging an insane four TDs for every ten long passes he throws. Eight out of his ten completions at that distance have gone for six points. He also has no interceptions at any distance all year -- the only quarterback with more than 75 passes who can say that. (No fumbles either.)
Even if the completion percentage stands, those most certainly won't. Last year, RGIII led the league in touchdown rate on passes of 20 yards or more -- at only 19.4%. Even if defenses don't significantly adjust their coverage schemes (although I expect they'll have to back out of the box more now), Foles simply can't count on the type of luck he's had so far with defenders falling down, receivers wide open, and more. He also eventually will start throwing interceptions. Last year he threw them on just 1.9% on all throws, but Football Outsiders' adjusted interception rate showed a more pedestrian 4.2% after accounting for defenders dropping would-be picks.
The first takeaway here is that SuperNick's current outsized numbers will almost certainly come back to Earth. He may be good the rest of the year, but he won't be that good. The second takeaway is more important, though. Foles' improvement is only over a small sample, but it may not be an anomaly. Kelly is putting his quarterbacks in a great position to succeed, and when defenses change to prevent that, it will only give McCoy more room to run. If the Chip's scheme looks this good with competent QB play from a limited upside guy like Foles, think about what it might do with a true top-tier talent at the position.