...mentality is "Let's go out, play crazy, try to outscore the other team, and throw defense to the wind." Although he has proven that system can work (except against teams that play slow and have good defenses - see Utah and Purdue), now that we suddenly don't have our leading scorer, my belief is this philosophy will likely fail. I guess we'll see over the next three games against decent opponents with Tyler out.
I don't know whether Rose's teams don't play defense because he doesn't know how to coach defense or whether he isn't interested in coaching defense. The lack of good big men excuse is legitimate to some degree, but not the point of how bad BYU's defense really is (and why do we continue to have such terrible big men?). You don't rank #312 of 345 teams (#340 prior to the Utah game) in scoring defense just because your big men are struggling. BYU defenders are regularly out of position, rotate too slowly, leave soft spots open all over the zone, let guards get to the paint on a consistent basis, and frankly ignore the fundamentals. This is definitely a "let's try to outscore the other team" mentality for defense.
On the flip side, a strong defense can keep you in games even with key injuries, which Utah has proven. I really wish Rose would go out and find a good defensive minded assistant. I honestly believe BYU would have several additional wins per year if they had some semblance of a defense.