Ahhhh.. OK so I interpreted "opponent" as their bowl opponent, not previous opponents throughout the season.
So I took oregon's offensive YPC and subtracted Liberty's defensive YPC allowed, and vice versa (Liberty oYPC minus Oregons dYPC). Comparing these caluclated values- if the underdog has the advantage (which I called a "positive differential") then that made them a play.
Hopefully there is still an edge to these teams.
Interestingly, I placed my bets soon after opening lines came out and many of them have become more favorable (meaning I got crappy lines)
I didn't see stats for the average opponent YPC and defYPC. May I ask where you get that data from?