A sophomore slump is easy to explain. It's a condition which has effected enough second-year players that it has become a well-known, oft-expected affliction.
Some guys will manage to avoid it, but most players do hit that proverbial wall at some point.
Why? The main reason is opposing defenses begin to familiarize themselves better with that guy's style of play.
See, the great thing about being new to a conference is that defenses aren't familiar with a player's tendencies yet. Film can only show so much—the real test comes on the field. Therefore, many times, a players speed, agility, and strength can be underestimated.
That said, upon first encounter, many defenses will be a bit unprepared. However, defensive coordinators don't get paid to only watch tape, they are paid to not be fooled twice, and that means, by the second time around, most defenses will have adjusted their schemes to impede a particular player's progress.
Once that happens, it becomes that player's job to adjust his tendencies again.
That is not done easily as many of these guys have been running, catching, juking, and cutting the same way for their entire lives. As a result, they simply cannot make those adjustments without seeing a drop in their production from the previous season—therein laying the foundation for the dreaded sophomore slump.
Even so, there are players who will be able to defy those odds and make a run at being even better than the year before—a sophomore superstar if you will.
In my opinion, these guys are primed to be even better players as sophomores than they were as freshmen.