Early in each NFL season, we see smaller point spreads as oddsmakers rely strongly on last year's power ratings to set their lines. But as more and more games are played, new, relevant data becomes available, allowing sports books to refine those numbers and understand the separation that exists between each team.
With a larger sample size, oddsmakers feel more confident posting larger point spreads, a trend we see more frequently as an NFL season wears on.
From 2003 to 2012, only 51 NFL games played in September closed with a double-digit point spread. However, that total more than doubled in December as the number of games with 10-plus point spreads increased to 119.
The table below illustrates this further:
Currently, there are three teams listed as double-digit underdogs for Week 6 (Jaguars, Cardinals and Titans). Because I expect double-digit spreads to become more common as the season progresses, I developed a winning betting system that not only can be implemented this week, but can be used as a baseline system every time we see double-digit underdogs for the rest of the season.