So far, the defense has definitely been a work in progress. It needs to improve--significantly--if BYU expects to have significant success this season.
The offense will likely be fine, especially if they learn how to hit free throws. But in order to really achieve their aspirations as a team the defense needs to get better. I'm not overly concerned yet, because it's a new coaching staff with lots of new players and they have seemed to be marginally better on defense in each game. So maybe it's just a matter of time and experience.
BYU will go as far as their defense allows them to.