By all accounts, Wyoming had a top-10 defense last year. 9th in defensive PPG given up; 23 for total yards fiven up; #1 in forced turnovers. Do you really think they're that good, or might their defensive ranking be a factor of their competition?

BYU's defense probably isn't the weak link, but I'm hesitant to ascribe their ranking all to talent. I think the same kind of thing is going on here. A lot of BYU's pass ranking has to do with facing weak passing opponents (with the exception of UW, and UW torched BYU).

It's also worth noting, if you're dead set on sticking to rankings, that USU's pass defense is currently ranked 22nd. So USU faces a better pass defense literally every day in practice when their offense goes against their defense.