[pitt1980]

http://www.advancednflstats.com/2010/06/bill-walsh-on-random...

In his early Stanford days, Bill Walsh had already cracked the code on how un-random football coaches (and almost all people) are. From "Controlling the Ball with the Passing Game":

"We know that if they don't blitz one down, they're going to blitz the next down. Automatically. When you get down in there, every other play. They'll seldom blitz twice in a row, but they'll blitz every other down. If we go a series where there haven't been blitzes on the first two downs, here comes the safety blitz on third down."

Most NFL offenses tend to alternate rather than randomize. Walsh knew defenses were just as predictable decades ago.