I think some of his dropoff can be attributed to external factors, but I am really disappointed in JC's defense this season. One of the reasons I was more optimistic about him is because despite his offensive role falling off, he did see progress as a defender over time in ATL. I think he got a lot tougher and competitive on that end, and this was shown in the numbers as well. In the playoffs in particular, he matched up with a lot of top level players. It didn't always go well, but he was a decent ish physical matchup against bigs like Bam and Randle as well as physical wings like Brown. Again, he wasn't great, but he was like a B level defender against a range of different players. That in addition to his rebounding made him a defensive asset.
This year, he just looks completely lost and doesn't even seem to try. Perhaps that's just Hardy's wack *** system, but I think he's looked really bad as an individual. We are so much worse with him (both ends) on the court. Walker Kessler isn't having a great year, but if we're playing one or the other, Kessler is clearly the superior option right now.