I think the biggest concern is that he's "played poorly" for about 80% of his career to this point. We've seen a consistent baseline for about three years and one peak for around 60-80 games last year. I said about three years ago I could see him turning into a Robert Lang type guy where you see immense talent, but only for about 15 games a year. The rest of the time he's sort of like existing and playing a nice game. While that's fine, it's not what you want from the 2nd overall. Not when the guy drafted behind him is going to average 100 points a year for the rest of his career.
A lot of us said he seemed to turn that proverbial corner and was deferring less and taking control more. I'm pretty disillusioned with the team so I haven't really watched at all this year, but it sounds like he's not so much regressing as he is settling back into what he really is. There's a huge list of players who looked fantastic next to Kopitar and then they struggle any time they weren't on his wing. Brown, O'Sullivan, Cammalleri, etc. Byfield wouldn't be the first guy. If he doesn't start playing like he did last year, I think it's safe to say he is what he is at this point.