Last season was his breakout season. And was exceptional.
That said, he is actually having a pretty good season. Not as good as last year, but still good enough.
I have some theories as to why -
1st - He was playing injured, and might have that in his head. Or still has a bit of discomfort.
2nd - Didn't he grow like 5-10cm in the span of half a year? I think he & and his body is still adapting to this growth.
3rd - His off the field antics had an impact. Good thing, he seems to be a bit private nowadays.
I am sure, come March high octane time, the guy will level up his form.