Second Half Breakdown: Why?

Everyone knows Michigan has really fallen apart in the second half of their recent games. But, this was also a problem last year. We finished 3-9, but we were winning at halftime of a lot of games. RR didn't have this problem at WVU. Michigan has changed DCs each year and that means "defensive half time adjustments" might not be the cause (unless Schafer and Robinson were equally bad at it). But, it also may indicate that a new system each year may be the cause. Anyway, based on the past two seasons, what would you say is the biggest reason for 2nd half meltdowns? 1. Lack of halftime adjustments (or bad adjustments). 2. Limited knowledge/experience with the DC's playbook and inability to effectively run other plays to counter other team. 3. The Barwis effect is over-hyped. 4. Young players choking. 5. Lack of depth for tired/injured players. 6. Better half-time adjustments by B10 coaches than in the Big East. 7. Lack of half-time motivational speech, etc... 8. Weird coincidence. 9. No one holds a candle to WVU's DC Casteel. 10. Other? Personally, I think it is almost all No. 2. At the beginning of the game, the defense looks somewhat confused and has busted coverages. They barely get the "base defense." So, I don't think they know enough to be able to adjust to other defensive plays during halftime of a game. Meanwhile, the other offenses can adjust. I also think No. 5, lack of backups, makes a difference when players need a rest in the second half. The others should not be the prbolem because they are either (a) somewhat constants from RR's time at WVU, or (b) improbable (i.e., I just don't think Big East coaches could be that much worse at half-time adjustments than weak B10 coaches.)