This hasn't been "clear" at any point in his career.
Nor is there anything to suggest that he's having any sort of back problems.
As for expectations for Lucic next year? Who knows... before Christmas he was on pace for 20 goals and 60 points.
What flipped the switch for him to go from having a pretty good year to being pure garbage? No idea. We can speculate as much as we want. But we should be expecting more out of the player than 40 points.
Well I think you're setting him up for failure if you're gonna expect that from him. He's at some point not going to be at that pace and probably start to panic again, then the same cycle starts where he begins to grip his stick too tight.
It's better to keep expectations low and in check. Also dude has a degenerative back condition, why is it not a good possibility that that is kind of kicking in?
The other problem with Lucic, he doesn't really ever have seemed to have great chemistry with any of the three centers. McDavid, no. Draisaitl, only once in a while. Ditto for RNH. There's no one on this team that he plays with even last year where he was better where you go "wow, they have great chemistry" for any extended stretch. He's just a bad fit on this team. Maroon was far better of a fit.