Here are five things we’ve learned about the Boise State football team a quarter of the way through the 2012 regular season:

1. The defense reloaded. The Broncos lost five defenders off last year’s team who are on NFL rosters, forcing them to start four sophomores and a freshman this year. And through three games, the defense has looked like one of the nation’s best. Opponents average 4.5 yards per play — down 13.5 percent since last year (5.2).

2. QB transitions are difficult. Junior Joe Southwick spent two years as Kellen Moore’s understudy, so there was hope the offense would click. Instead, the unit has experienced the hiccups that strike so many that have to replace an elite quarterback (see: Stanford). The biggest obstacle has been Southwick’s inability to throw touchdown passes in the red zone (one in 12 drives). Worth noting: The Broncos failed to score 30 points in three of Moore’s first six starts (2008), two of Taylor Tharp’s first three starts (2007) and three of Ryan Dinwiddie’s first five starts (2001).

3. Some kicking issues remain. Senior Michael Frisina has restored some sanity to the kicker position — he’s 6-for-6 on PATs and only one of the two missed field goals was his fault. But the Broncos haven’t made a field goal longer than 32 yards since Kyle Brotzman’s 50-yarder on Nov. 19, 2010, against Fresno State.

4. Youth is served only on defense. While the Broncos have received significant contributions from previously unproven players like sophomore defensive end Demarcus Lawrence, redshirt freshman end Sam Ukwuachu and sophomore cornerback Bryan Douglas, the offense has relied almost exclusively on veterans. Every offensive starter except one — sophomore wide receiver Matt Miller, who is a returning starter — has been a junior or senior. Southwick is the only offensive player to get his first career start this season. Tailback Jack Fields leads the freshman class with 51 offensive yards.

5. Expanded Bronco Stadium is loud … really loud. “The guys would come back to the sideline and say, ‘Did you hear the crowd? Did you hear the crowd?’ ” sophomore linebacker Blake Renaud said of the BYU game. “… We were having so much fun out there.” Next home game: Oct. 13 vs. Fresno State (1:30 p.m.)