BYU's defense ranks 4th in the nation, according to the latest S&P+ statistical rankings from Football Outsiders.
If you aren't familiar with S&P+, it's a ranking developed by Football Outsiders to account for more than just yards and points gained, scored, and allowed. It factors in success rate of plays, points per play, and strength of opponent. So in addition to how many yards a defense gives up, it accounts for how many yards the defense should give up to the given opponents on the schedule.
On overall defensive ranking, BYU trails only Alabama, Oregon, and LSU. Before the Boise State game, BYU's defensive S&P+ was 6th. When looking specifically at stopping the run, S&P+ says BYU is second only behind Alabama.
The offense, however, is a different story. The Cougars rank 108th out of 124 FBS teams in offensive S&P+.
According to the S&P+ measurement, Hawaii comes to Provo with the 82nd-best offense and the 112th-ranked defense.