The NFL's shift toward the passing game has been an indisputable notion for years. So what is different about the first two weeks of the 2013 season? This, my friends, has been a trend on speed.

We've seen history made and once-in-a-generation performances rendered commonplace. Rushing totals are at a 12-year low, but you won't hear complaints from either the league office or television networks.

The highlights:

The league set single-week records in total passing yards (8,143) and touchdowns (63) in Week 1. Through two weeks, teams have passed for 16,355 yards and 111 touchdowns, the most-ever over that span.

Five quarterbacks have thrown for at least 400 yards in a game without an interception, one off the record for an entire season. (It happened six times in 2012 and 2010.)

There have been more than four times as many 100-yard receivers (38) as 100-yard rushers (nine) through two weeks. (And one of those 100-yard rushing games was by a quarterback, the Oakland Raiders' Terrelle Pryor.) That differential of 29 is by far the highest over the first two weeks of any NFL season, according to the Elias Sports Bureau. The largest differential before this season was 19 in 2011.

Teams have combined for 36 rushing touchdowns and an average of 3.8 yards per carry, the lowest such marks through two weeks since the 2001 season.

Is this the simple result of scheme development over time? Or has the NFL effectively made the pass impossible to defend? ESPN's NFL Nation spent Wednesday asking questions around the league's practice facilities. Here are some of the answers: