its almost like, the sophmore slump kind of exists. and injuries screw stuff up too
everyone who wrote him off last year, you were wrong!
Sophomore slump might be one of the most annoying cliches in sports. Yes, some sophomores struggle, but it isn't disproportionate to a player going from year 2 to year 3 and so on. Dramatic decreases on a players average return can happen in any year. Look at our big rookies from 2015/16. The only ones who notably decreased from one year to the next were Zaitsev and Brown. Everyone else stayed stagnant or produced at a better level. In Brown's case, that was partially influenced by a change in usage. Matthews, Marner and Hyman produced better, and Nylander was pretty much stagnant.
Now, sometimes they seem more extreme because the rookie year was a mirage and the player never regains that form. Notable cases of this are RNH, Yakupov, and Tyler Myers. So, their rookie season production wise was actually the outlier in their career. In most of these cases, there are clear analytics you could point to which caused this.
Now, I obviously hope you are right about Zaitsev bouncing back, but I don't think it had anything to do with him being a sophomore. It is more likely the latter stuff you mention which was injuries.