The idea that anyone thinks that freshmen automatically improve when they become sophomores is a strawman.
Of course some players get worse as sophomores. Most, however, get better. The idea that players improve the most between their frosh and soph years is one of those widely accepted axioms that actually holds up under statistical scrutiny.
Big Ten Geeks summed it up well: "The big, overarching conclusion is this: a player shows the most improvement between his freshman and sophomore seasons than he does any other offseason. In fact, the freshman offseason improvement is, on average, greater than the improvement between a player's sophomore season and his senior season. That's not to say every player follows this pattern. There are lots and lots of exceptions, and this is no hard-and-fast rule. It's just a remark about the averages. And frankly, that's all we do around here, play the averages."
I found a
Michigan State blog post that pulled out an excellent table from one of the Basketball Prospectus books:
Applying those numbers to our 8 freshmen (including DGreen), we should expect 1 player to significantly regress, 2 players to slightly regress, 2-3 players to slightly improve, and 2-3 players to significantly improve.
On the whole, it is safe to assume significant improvement from our rising sophomore class, despite the fact that it is unlikely they
all improve.